A citation (or reference) records the information necessary to finding the sources you consulted in your research. Common elements include the author's name, the year of publication, the publisher, the title of the journal in which an article was published, and the title of a book. In general, it is appropriate to cite the materials consulted in your research whenever they are used in your own work. Use of another's work could take the form of any of the following:
Providing a citation serves a number of purposes. By properly attributing ideas, opinions, and statistics to their authors, you avoid taking undeserved credit for them (plagiarism). It also allows the reader to confirm that you are representing others' work accurately. Finally, it serves as a starting point for those who are interested in exploring the topic further.
The American Medical Association Manual of Style lays out the most widely accepted principles of medical writing. It covers a broad array of topics, including referencing, grammar, scientific writing, ethics, and more. The AMA Manual of Style is a reference work and, as such, most of the information contained in it should be consulted on an as-needed basis. However, any student in a medical program will need to know how to correctly apply the AMA's Referencing System (Chapter 3) to cite sources of information used in their research. Click the link below to go directly to the AMA Manual of Style.
The American Medical Association Manual also has its own blog. If you are looking for clarification on something that is not explicitly treated in the AMA Manual, Style Insider is a great place to look for guidance.
For better or worse, the AMA Manual of Style is also on Twitter! If you would like an authoritative answer to something that you aren't able to find in the good book, you can tweet your question directly at them. You can also follow them at @AMAManual if AMA Style mastery is your goal.