If you are writing for publication, check out Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers on the Library Web site or at http://www.nlm.nih.gov/citingmedicine.
This electronic book (ebook) provides guidance to authors in compiling lists of references for their publications. The increasing number of publication formats, such as those available on the Internet, has made the task of compiling reference lists more complex. This book aims to ease the work of authors and editors by applying existing bibliographic standards to complex biomedical publications. The book also documents the National Library of Medicine’s own rules for the structure of citations as used in its MEDLINE / PubMed database.
For more information on Citing Medicine, including its source material and structure, see the book’s introduction. The NLM intends Citing Medicine to be an evolving publication. You are invited to join the CITINGMED LISTSERV to learn of addtions and changes.
Citing Medicine updates and supersedes two previous NLM electronic book publications:

• National Library of Medicine recommended format for bibliographic citation, 1991
• National Library of Medicine recommended format for bibliographic citation. Supplement, Internet formats, 2001.