Searching the literature and selecting the right references.

The ability to locate published data on a topic is a fundamental skill in the research process, and it aids in formulating and refining a research question and planning the study. Searching the literature for published studies on a topic relevant to one's question requires knowledge of databases such as MEDLINE, Cumulative Index to Nursing and Allied Health, or Hospital Literature Index. PubMed provides access to MEDLINE and over 12 million citations in the medical literature. When searching in PubMed you can apply various "limits," such as what fields the search term is in (eg, author, title, text word, journal), type of report (eg, clinical trial, review, editorial), language, patient age, gender, and human or animal study. The "Boolean operators" (AND, OR, and NOT) can further focus and refine your search. However, to be sure that you retrieve all the files of interest and don't miss any files that might be critical to your understanding of the topic, you must search all fields and be careful not to exclude potentially important files with the NOT operator.