AMA Style Guide

References are numbered in  consecutive order in the text, tables, or figures.

Use superscript arabic numerals to cite material, e.g., ¹    The first reference used in a written document is listed as 1 in the reference list.

Where to place the superscript?  The superscript number ¹  is inserted into the document immediately next to the fact, concept, or quotation being cited.  If citing more than one reference at the same point, separate the numbers with commas and no spaces between. 

The Superscript number is inserted:

• Immediately next to the fact, idea or quotation being cited.  Ex. This drug is used to treat hepatitis.¹
• Outside periods and commas. Ex. Storing latex at high heat may cause degradation, ^2,3-5,7  but it is difficult to keep materials cool in a desert environment.
• Inside colons and semi-colons. Ex. Some physicians choose to store prescription pads in locked cabinets ⁸; others keep them in their coats at all times. ⁹
• When more than 2 references are cited at a given place in the manuscript, use hyphens to join the first and last numbers of a closed series; use commas without space to separate other parts of a multiple citation.  Ex. As reported previously,^1,4-7,19,24

If a reference is used multiple times in one paper, use the same number throughout.

At the end of the document, include a reference list with full citations to each item. Name it References. Order citations as they appear in your paper.

Using author's names in-text: You may use author names in your text, as long as these mentions are accompanied by numbered citations. Use last names only.  For items with one or two authors, include both names. For items with 3 or more authors, include the first author's surname and then 'et al' or 'and colleagues'.

Ex. Smith and Jones² reported on the questionnaire. Ex. Hammersmith et al³ reported on the survey.

Secondary Citations:

 The AMA Manual. section 3.13.10 Secondary citations, states:  Reference may be made to one author’s citation of, or quotation from, another’s work. Distinguish between citation and quotation (ie, between work mentioned and words actually quoted). In the text, the name of the original author, rather than the secondary source, should be mentioned. (See also 3.11.12, References to Print Journals, Discussants.) As with citation of an abstract of an article rather than citation of the original document (see 3.11.9, References to Print Journals, Abstracts and Other Material Taken From Another Source), citation of the original document is preferred unless it is not readily available. Only items actually consulted should be listed.
    Ex.  Cauley JA, Lui L-Y, Ensrud KE, et al. Osteoporosis and fracture risk in women of different ethnic groups. JAMA. 2005;293(17):2102-2108. Cited by: Acheson LS. Bone density and the risk of fractures: should treatment thresholds vary by race [editorial]? JAMA. 2005;293(17):2151-2154.