Skip to Main Content

KansasCOM Library

What would you like to find at the library today?

OneSearch for Everything
OneSearch for Journals
OneSearch for Books
OneSearch for Peer-Reviewed Journals

eTextbooks 2023-24

eTextbooks for 2023-2024:  Years 1 and 2

You may access all of the available eBook versions of your textbooks here. Links will take you to the record in the library catalog where you may access the content by clicking on the available link. For best results, please login to your library account before accessing eBook links.

The KansasCOM Library recommends creating a personal user account within each of the eTextbook portals. Creating a personal account will open additional resources to you such as the ability to bookmark and access practice questions. Click on the tabs to explore the eTextbook resources for your learning tracks.

Check out our eBook App & Help tab for information about creating personal accounts and downloading apps to use on your smartphone or tablet.

  • For the best experience using links to eBooks and other resources in your Canvas and ScholarRX assignments we recommend using Firefox, Microsoft Edge or Safari if accessing using a desktop or laptop.

If you encounter any issues or difficulty accessing eTextbooks, please let the library know as soon as possible!


The KansasCOM Library strongly recommends students create personal user accounts with each of these services.

The majority of eTextbooks are located in three collections:

Additional eTextbooks are also located in these databases:

Why Create a Personal Account?

While there are multiple benefits to creating a personal account, there are two benefits that will impact your use of the eTextbook platforms:

  1. Ability to create bookmarks
  2. You'll need a personal account to use vendor apps on your phone or tablet

The KansasCOM Library recommends using your student email address to create your accounts but you may use any valid email address to set-up your accounts. Most of the library resources require you to complete the set-up by clicking a link provided in an email.

Typically, you will find the registration and login links in the top right corner of the database or resource collections.

Our eTextbook collections offer a variety of services beyond just the text needed for reading assignments. Below is a table where you can see exactly what is available in each.

Although two of three platforms have an app, all are optimized to display on your device (laptop, tablet or phone) and adjust to fit your screen. The KansasCOM Library recommends viewing through a web browser for the best performance/use of the materials.

  • Available apps are linked below!

Special Features in eBook Platforms
  AccessMedicine ClinicalKey LWW Health Library


Board Review tools X
Case studies X X X
Clerkship/Clinical Rotation resources X X
Clinical Practice/Guidelines X
eBooks X X X
Flash Cards X
Images,  graphs, charts, etc. X X X
Journal clubs X
Journals X
PDF file downloads (chapters/books/articles) X X
Podcasts X
PowerPoint slides X X X
Practice Tests/Self Assessments X X
Videos X X X

Reading Tips

Reading loads can be very heavy in medical school. Even blue light reading glasses or filters can't always ease that. Below are some solutions to help out and provide alternatives to reading on your laptop screen. 

If you have figured out other alternatives, please share so we can add them to the list!.Audio Readers

Two of our textbook platforms incorporate AI readers for you to use. They are as simple as clicking 'play' in the book you happen to be reading. Here are some screen shots so you know what to look for!


LWW Health Library

Tablets or Smartphones

Whether you are an android or apple user, you will be able to access our resources and be able to read on your handheld device. Our websites are designed to adjust to the scale of your device to make reading a little bit handier. 


PDF Downloads

Some of our textbook platforms allow you to be able to dimply download pdf files of chapters and some need a little bit of work-around to accomplished this. Whether you are planning to print or annotate the pdf file, here are easy tips to obtain them.


Reading from a screen can get tiring whether or not you battle dry eyes. Sometimes you just want a printed copy to make notes or to be able to easily backtrack and re-read sections of the text. Downloading pdf files from textbooks is pretty straightforward, but sometimes there is no pdf download option and you really want to print. Highlight the text you want and send to the printer, or you may opt to download as a print to pdf option to save and then print when needed.  See the examples in the section above for more details.

**It is permissible for you to print without fear of copyright violation from the library resources.

Online Readers

There are a variety of free online readers available. Some require registration or a download. Some only require an internet connection to work. All vary depending on the way you want to provide the content.

You can use the links provided below to copy and paste text into the free reading software options. Nearly all of the services offer a 'free' version that requires no sign in or service fee to use. The options are pretty basic but are also adequate to just have the service read the text you want. They all offer a subscription version that offers more options and it is up to you to pay if you choose to subscribe.

I was able to find these options when I Googled 'text to speech free'. They all work in very similar ways.

Links to eTextbook Platforms

Required Texts
Supplemental Texts
Gross Anatomy
Neuroscience & Neuroanatomy
Additional Resources
Required Texts
Supplemental Texts
Required Texts
Supplemental Texts

Resources Spotlight

New England Journal of Medicine

Full-text coverage from 1990 to current issue.


Evidence-based Clinical Decision Support

Access Medicine & Case FIles

Core medicine and science textbooks

Bates Visual Guide to Physical Examination with OSCEs

Head-to-toe and systems physical exam videos


Clinical Search engine and point-of-care database

LWW Health Library: Osteopathic Medicine Collection

The Osteopathic Medicine collection is a combination of 7 authoritative references eBooks ideal for professional practice and educational curricula, PLUS roughly 450 clinical videos demonstrating critical manipulative techniques.

LWW Health Library: Premium Basic Sciences Collection

Interactive online access to 35 textbooks on core/fundamental topics, plus procedural videos, images, real-life case studies, and quiz banks for medical and health science students and practitioners.



PubMed comprises more than 29 million citations for biomedical literature.

JAMA Evidence

Evidence-Based Instructional resources from the American Medical Association

JAMA Network

JAMA Network

Full text access to the full suite of JAMA publications and education tools.

Access Pharmacy

Core Pharmacy Textbooks

MEDLINE Ultimate

Full-text database of biomedical and health journals.

Acland's Video Atlas of Human Anatomy

Human anatomical specimens in real-life 3D.


Interactive human anatomy atlas.

Visible Body

Virtual Anatomy Learning site

Cochrane Library

Cochrane Library

The Cochrane Library is a unique source of reliable and up-to-date information on the effects of interventions in health care.

First Aid USMLE

A collection of eBbooks designed to help prepare students for the USMLE.

Anatomy - MedOne Thieme Teaching Assistant Anatomy

MedOne Thieme Teaching Assistant Anatomy is a presentation tool featuring 2000+ full-color illustrations and clinical images from Gilroy et al.'s Atlas of Anatomy and additional images from Baker et al.'s Head and Neck Anatomy in one platform.

Getting Started with Research

Even if you have done research in the past using library resources or other search engines such as Google Scholar, beginning to understand and conduct medical research can be daunting. While many of the principles for searching are similar, the resources can be very different. Analyzing research articles and studies is a more involved process than simply finding something you can use as evidence in a research essay.

Locating research studies as first steps for a literature review in the overall research process is more involved and finding relevant research studies when investigating treatment options can be even more involved. The information located in this box and organized using different tabs is intended to serve as an introduction to these research processes. As a student doctor, you aren't expected to already know everything, but are on a journey to becoming a practicing physician. Part of that journey is to gain an understanding of how to conduct medical research.

Our library staff is here to assist you in this process and to help you learn how to do good quality research.

Download this file to access KansasCOM poster templates.

Are you preparing to present at a conference or other event? These KansasCOM themed poster templates are just what you'll need to get started.

Tips for Creating Your Poster

  • We recommend downloading the KHSC-KansasCOM poster templates with school logos/colors on them. There are three templates that have pre-labeled sections to aid in formulating and formatting content. This is a great time saver. 
  • Basic DO's and  DON'T's
    • DO's
      • identify resources
      • plan poster
      • be brief & to the point
      • select contrasting colors
      • select an easily readable font
    • DON'T's
      • use ALL CAPS
      • have more than 10 words in your title
      • use more than 2-3 contrasting colors
      • procrastinate
      • use paragraphs or large blocks of text
  • The Seven S's of Success
    • Story
      • just as with any story you write, a poster should contain a title, beginning, middle and conclusion
      • keep in mind that our eyes are trained to read content left to right, top to bottom, in columns
    • Style
      • visual appeal: catch the reader's eye
      • manageability: overview of message, don't be too detailed
      • hierarchy: use headings, color, text and images to showcase important information
    • ​​​​​​Simplicity
      • decide upon one style for your images, graphics, and photos
    • Size
      • use fonts and images that are easy to read and interpret, don't go microscopic!
    • Statistics
      • use research, articles, and statistics to support your information; make sure they are current, reliable and on topic
    • Sources
      • ​​​​​​​use quotes and give credit to your sources to establish credibility
    • Shareability
      • ​​​​​​​provide readers with tools they need to follow up for more information


  • Briggs, D. J. (2009). A practical guide to designing a poster for presentation. Nursing Standard, 23(34), 35-39.
  • Crane, B. E. (2016). Infographics: A practical guide for librarians. Lanham, MD: Rowman & Littlefield.
  • Miller, J. E., & Bloustein, E. J. (2007). Preparing and presenting effective research posters. Health Services Research, 42(1P1), 311-328. doi:10.1111/j.1475-6773.2006.00588.x
  • Persky, A. M. (2016). Scientific posters: A plea from a conference attendee. American Journal of Pharmaceutical Education, 80(10), 1-3.
  • Rose, T. M. (2017). An illustrated guide to poster design. American Journal of Pharmaceutical Education, 81(7), 1
  • Siedlecki, S. L. (2017). How to create a poster that attracts an audience. AJN American Journal of Nursing, 117(3), 48-54.
  • Taggart, H., & Arslanian, C. (2000). Creating an effective poster presentation. Orthopaedic Nursing, 19(3), 47-52.

Library Account Login

You can search the library catalog, One Search, from anywhere you have internet access. You will see results whether or not you login to your account. You will need to login to your library account to see the full results for any search. It is a good idea to establish a habit of logging into your account. Your login information is the same one you use to access the student portal and all other KansasCOM resources such as email and Canvas. (Single sign on, SSO).

By logging in to your library account you will be able to:

  • Save searches
  • Save search results
  • Easily submit interlibrary loan requests: Article copies

  • To begin your search, enter your search term:

  • You will likely get too many results! Our library has millions of digital article and book records available.

  • Using the 'Advanced Search' you can enter additional search terms to be more specific and reduce the number of results

  • Once you have narrowed down your search you can:
    • Save your search
    • Examine individual results by selecting the title
    • View the full text, cite, save the item to your account, and more!
  • Use the push pin to save the item, select 'Save Query' to save your search
    • Saving searches is handy if you don't have time to examine your results or if you want to re-use the search later and see any new results that may have been added

Medical Databases & Resources

Beyond the textbook collection, the KansasCOM Library offers access to other medical databases and collections. Below is a list of these along with links and a brief description of what may be found in each collection. 

As with the textbook collections, we recommend creating a personal user account. If you have questions or need assistance, please contact the library!


Knowledge for Practice, Professional Communication, Scientific Literacy, and Communication Skills are all important competencies for medical practice. Learn more about the Physician Competency Reference Set (PCRS) here.  Conforming to the required academic writing form and style for various journals is a means of demonstrating competency in these domains.

The official writing style for KansasCOM is the National Library of Medicine (NLM) citation format. This format was selected because it is the most-used citation format for professional journals in the field of medicine, and is the selected format for MEDLINE/PubMed citations. Faculty, students, practitioners, and administrators must use common citation formats. Failure to adhere to required citation styles interferes in understanding for the reader and conveys a general lack of professionalism that may interfere with how the writers message is received. Failure to adhere to required citation styles may result in major funding opportunities being lost, particularly with large federal grants in medicine and science.

While you may be familiar with other citation styles such as APA or MLA, you will find that the principles with NLM style are similar. Repeated use and practice will help you to acquired the necessary skills to successfully cite. The KansasCOM Library provides you with tools to assist you and this section of our webpage is intended to do so.


Refworks will help with keeping track of resources you have read and plan to cite when writing. Organizing citations is easy and downloading your references in NLM style is an easy-to-use feature. You may also opt to connect your RefWorks account to Microsoft Word to easily cite as you write!

KansasCOM has an active site license for RefWorks (through our TCS Education Affiliation) in order to provide our community with a fully functioned, and fully supported, reference management solution.

RefWorks allows you to save, organize, deploy, and share references in a variety of ways.

  • Collect references from a variety of sources and store them in a single location
  • Organize references in folders and sub-folders by topic
  • Format and create bibliographies in NLM Style
  • Share folders of references with colleagues and project partners
  • Insert citations into your papers with Microsoft Word or Google Docs

To register for a free account​ you must use your KansasCOM email address:. (i.e. ****, and click on the "Create Account" link from the RefWorks Login Page

Catch how-to videos on the RefWorks Youtube channel in order to take full advantage of your account.

Download our RefWorks registration guide: 

  • Once you have created your account, it's a snap to add new items to your collection. Clicking on 'RefWorks' in the library catalog is the best way to add high quality citations to your collections. While RefWorks is fairly intuitive to use, the videos on the YouTube channel provide a quick start to maximize your use and to help you set up your account to take advantage of provided tools.
    • Set NLM as your preferred citation style, you can easily switch between various styles
    • Upload your citations from other citation platforms
    • Integrates with Microsoft Word, allowing you to cite as you write
    • Create folders to stay organized
    • Add the 'Save to RefWorks' tool to you browser toolbar
    • and so much more!

The tool to integrate with Word is already install and waiting for you to connect your account

Access the open access citation manual:

SAGE Research Methods is a great way to learn about research, creating and planning your research projects and even search for funding. Highlights include:

Why Publish?

Providing a solid CV that demonstrates your commitment to research and academic excellence can play a vital role in your match for residency and other post-graduate experiences. Fortunately, publication experience dating back to your time as an undergraduate can be listed. It can be daunting to look at the average number or publications for various specialties and you may worry you won't be competitive. There are multiple experiences you can take advantage of during your time as a medical student. However, this information is intended for those seeking to publish in professional journals. 

What counts as a publication?

  • peer-reviewed journal articles/abstracts
  • peer-reviewed journal articles/abstracts (other than published)
  • peer-reviewed book chapter
  • scientific monograph
  • poster presentation
  • oral presentation

There are three main types of articles you may choose to write:

Remember, librarians can help with literature reviews!

Where to Publish

There are many well regarded publications that focus on student research and others that welcome submissions by medical students. This list is not intended to be comprehensive of every publication, but a place to begin. The links will take you to the publisher's author requirements which will provide needed information when preparing a manuscript for submission. An additional note has been added if the publication is available in our library. 

Be sure to login to your library account in One Search. It's as easy as logging in to your library account.

Visit our 'Explore One Search' webpage for more information.

Explore our vast library of online resources

Be sure to create your account in BrowZine. It's as easy as logging in to your library account.


If you've searched using any kind of database or even only used a search engine, like Google or Bing, you should have some idea about how to search using the KansasCOM Library. Even if you haven't, the basic features should be a little intuitive.

Ultimately, the library staff encourages you to reach out for help as needed. We are here to help you understand how to search for research studies, background information, practice guidelines and about anything else you may be interested in locating.

Tips for Searching Library Resources

  • Use advanced search features when possible to limit your results
  • Use one word or term or phrase per search blank to search more effectively
  • Use tools to limit your results; these are things like: language, dates, resource type (usually located in a menu bar on the left side of the screen)
  • Take advantage of using Boolean operators when searching: AND, OR, NOT
    • AND limits results to those that contain all of the search terms you have used
    • OR broadens your search to include everything that mentions any of your search terms
      • this can be helpful if you're not sure what terms might yield results
    • NOT excludes results that contain terms you want to avoid in order to limit your results
    • If there aren't drop-down menus for Boolean operators and only one search blank is available, enter the operators between search terms in ALL CAPS
      • Usually you will see multiple search blanks when you elect to do an advanced search

Check out the information about Evidence-Based Medicine and searching farther down on this webpage for specific help with medical research

Set-up an appointment with the library's medical librarian for assistance with searching. Consult our expert researcher! See the 'Schedule an Appointment' box on the left.

What is Interlibrary Loan?

Interlibrary loan is a service offered to our students, faculty and staff to help locate and borrow resources that are not held by the KCOM Library. Interlibrary loan allows the library to help locate materials and request that they be sent digitally (when available) to be delivered to your email.*

Who can use Interlibrary Loan?

Currently the only eligible individuals able to take advantage of Interlibrary loan are the following:

  • All students, faculty, preceptors and staff on campus or remote
  • Alumni and Library Guests are not eligible to use the interlibrary loan service

A Quick Guide for Using Interlibrary Loan

  • Step One

  • Search for your item in OneSearch, the library online catalog
  • If the item does not come up in your search in OneSearch, click on "expand your search" at the top of the page:

  • Step Two

  • Locate the item and click on "Get it for me from other libraries"
  • If promoted, please "sign-in" using your KSCOM email address and password
  • Once signed in, click on the "Get a digital copy:" icon:
  • Click "Get it"
  • Follow the status of your request by checking your library account.
Watch your email
  • Digital items are delivered via your **** email account
  • Articles and chapters usually arrive in your inbox within 24 hours
  • The email will contain a download link
  • Please contact the library directly if you have questions

What Can and Can't Be Requested?

Please note that only articles and book chapters requests will be processed at this time. If you are interested in borrowing a physical item such as a book, please contact the librarian.
We can request... We cannot request...
  • Journal articles
  • Magazine articles
  • Dissertations
  • A Single Book Chapter*
  • Books or eBooks
  • Whole Journal Issues
  • Streaming Videos
  • More than One Book Chapter**
*For both physical and electronic books **This is due to copyright restrictions

For information about borrowing physical print materials such as books, please contact the librarian.

Research & Evidence-Based Medicine

Evidence-based practice is the integration of scientific evidence, patients' values, and one's own clinical judgment in order to make the best possible health care decision.


Sackett defines evidence-based medicine as "the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research." (Sackett, D. Evidence-based Medicine - What it is and what it isn't. BMJ 1996; 312:71-72.)

Please note: This guide uses the phrase evidence-based medicine (EBM) interchangeably with evidence-based practice (EBP).

Evidence-based medicine is at the intersection of clinical judgment, relevant scientific evidence, and patient values and preferences.

1. ASK - Convert the need for information into a focused clinical question. Use the PICO framework. 

2. ACQUIRE - Track down the best evidence with which to answer that question.

3. APPRAISE - Critically appraise the evidence for its validity, impact, and applicability.

4. APPLY - Integrate the evidence with your clinical expertise and your patient's characteristics and values. 

5. ASSESS - Assess the results of your intervention. 

Two Cardinal Rules of EBM

  1. Not all evidence is created equal - A hierarchy of evidence guides clinical decision-making.
  2. Evidence alone is never enough - Competent physicians balance risks and benefits of management strategies in the context of patient values and preferences.

  Additional Information Sources

This seven module introduction to Evidence-Based Practice research is key to understanding the value and process for locating high-quality research studies. The modules are self-paced to allow you to fully understand the principles presented and apply them to your own research.



© 2019 Duke University and University of North Carolina at Chapel Hill. This is an open-access publication distributed under the terms of the Creative Commons Attribution-NonCommercial-Share Alike license.

Experimental vs. Observational Studies

An observational study is a study in which the investigator cannot control the assignment of treatment to subjects because the participants or conditions are not directly assigned by the researcher.

  • Examines predetermined treatments, interventions, policies, and their effects
  • Four main types: case seriescase-control studiescross-sectional studies, and cohort studies

In an experimental study, the investigators directly manipulate or assign participants to different interventions or environments

Experimental studies that involve humans are called clinical trials. They fall into two categories: those with controls, and those without controls.

  • Controlled trials - studies in which the experimental drug or procedure is compared with another drug or procedure
  • Uncontrolled trials - studies in which the investigators' experience with the experimental drug or procedure is described, but the treatment is not compared with another treatment

Definitions taken from: White SE. Basic & Clinical Biostatistics. 5th ed. New York, N.Y: McGraw-Hill Education LLC; 2020.Retrieved April 21, 2022 from AccessMedicine

Levels of Evidence Pyramid

The levels of evidence pyramid arranges study types from hierarchically, with filter information sources, i.e. meta analyses, systematic reviews, and practice guidelines at the top, and unfiltered information, i.e. randomized controlled trials, cohort studies, case-control studies, and case reports at the bottom.

Not all resources in pyramid are available at the KansasCOM Library. Check with Library staff for assistance, access the list below, or visit the full database list.

Links to Evidence Based Medicine Resources

The KansasCOM Library provides access to most of the resources identified on the Levels of Evidence Pyramid. The links below will take you directly to those resources.

Meta-Analysis & Systematic Reviews

Critically Appraised Topics

Randomized Controlled Studies, Cohort Studies, Case Control Studies, Case Reports/Case Series

Background Information & Expert Opinions

PICO may be a new way for you to think about and search for research information. You may consider using this worksheet to help develop your PICO question. Even experienced researchers rely on tools like this when beginning research!

The PICO format helps you

  • form an appropriate, focused question
  • identify key concepts and brainstorm search terms
  • develop a strong search strategy
  • obtain a manageable number of pertinent results
  • appraise results for relevance

Adapted from Developing a PICO Question Tutorial: Part 1 of a 2 part tutorial series from Marymount Library's PICO Tutorials. 

The PICO model can help you formulate a good clinical question. Sometimes it's referred to as PICO-T, containing an optional 5th factor. 

P - Patient, Population, or  Problem
  • What are the most important characteristics of the patient?
  • How would you describe a group of patients similar to   yours?
  • What is the problem to be addressed?
  • Think of this element as the dependent variable
I - Intervention
  • What is the relevant treatment or exposure? What action or change would affect the patient/problem/population?
  • What do you want to do for the patient (prescribe a  drug, order a test, etc.)?
  • Think of this element as the independent variable
C - Comparison
  • What is the main alternative to compare with the intervention? (A different intervention? The usual standard of care? Not intervening at all?)
  • Think of this element like a "control group"
O - Outcome
  • What do you hope to accomplish, measure, improve, or affect?
  • Think of this element as what is measured to show what the intervention has accomplished or improved
T - Time Factor,  Type of Study  (Optional)
  • In what time frame should the intervention achieve the outcome?
  • What would be the best study design to answer the PICO question? 
  • Think of this element as additional, optional constraints to narrow the question

Foreground and Background Questions

Clinical questions are categorized as background or foreground. Once you determine your question type you may want to use the "Asking PICOT Questions Template" document to develop your question.

Background Questions

  • Ask to obtain general knowledge about an illness, condition, or disease
  • Ask who, what, when, where, how, or why

Foreground Questions

  • Ask for specific knowledge to inform clinical decisions
  • Deal with specific patient or population; more complex than background questions

Framing a PICO Question

Foreground questions can be further classified into four groups: diagnosis, therapy, prognosis, and etiology/harm. Certain study designs are better for answering particular question types. 

  • The "Appropriate Study Types" column lists study designs best suited to each question type, in order of utility.
Question Type Definition Appropriate Study Types
Diagnosis Questions addressing the act or process of identifying or determining the nature and cause of a disease or injury through evaluation

Randomized Controlled Trial

Cohort Studies

Therapy Questions addressing how a clinical issues, illness or disability is treated

Meta or Systematic Reviews

Randomized Controlled Study

Cohort Study

Prognosis Questions addressing the prediction of the course of a disease

Cohort Study

Case Control Studies

Case Studies

Etiology/Harm   Questions that address the causes or origin of disease, the factors which produce  or predispose toward a certain disease or disorder

Cohort Study

Case Control Studies

Case Series

Getting Started with Searching

  • Consider downloading the template above as you begin to learn to ask PICO questions. In addition to the four main types of questions, two additional types of questions listed that will help guide you in this process. The second page of the document provides short definitions for the type of questions along with samples of questions.
  • Consider using PubMed for searching. They have set up clinical queries that filter your results to aid in your searches.
  • Consider watching this video that shows how to search and limit your results in PubMed.
  • Consider watching this video that shows how to search for the full text of articles not freely available in PubMed.

Adapted from:

Research Assistance

Whether you are a novice or a veteran researcher, a little assistance can be critical for achieving successful results. Our library staff has extensive education and experience in utilizing databases. We understand the unique qualities of every research request and will be happy to help you through the process.

  • Use our 'Research Request' form to tell us a little about your research needs and suggest a meeting time or use the appointment scheduler located in the menu to the left.



Searching PubMed is often considered essential for medical health professionals and researchers. Research articles indexed using MeSH form a subset of the PubMed database, MEDLINE, and are included in One Search. There are specific search tools and methods that are particular to PubMed that do not translate well to that search interface. Because there are multiple ways to search using PubMed it is important to understand the basics of searching. The videos below will help you to navigate this resource and access full text articles.


You can use these links to connect directly to MEDLINE or PubMed:

Keep in mind, our medical librarian is always here to help you! You can create an appointment to meet virtually or in-person by clicking the link below.

This excellent video series from Welch Medical Library @ Johns Hopkins University demonstrates how to use PubMed effectively to build an advanced search.