AMA = American Medical Association
AMA is a standard format for medical research, health sciences research, and some other areas of scientific research.
The current edition is the 11th edition, so make sure you format your citations in the appropriate edition format that your instructor or professor requests.
AMA Manual of Style [10th edition] by 
Cite Right : A Quick Guide to Citation Styles - MLA, APA, Chicago, the Sciences, Professions, and More by 
AMA Style Guide by 