Each reference should be cited in the text, tables, or figures in consecutive numerical order by means of superscript arabic numerals. It is acceptable for a reference to be cited only in a table or a figure legend and not in the text if it is in sequence with references cited in the text. For example, if Table 2 contains reference 13, which does not appear in the text, this is acceptable as long as the last reference cited (for the first time) before the first text citation of Table 2 is reference 12.
Use arabic superscript numerals outside periods and commas, inside colons and semicolons. 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.
As reported previously,1,3-8,19
The derived data were as follows3,4:
Avoid placing a superscript reference citation immediately after a number or an abbreviated unit of measure to avoid any confusion between the superscript reference citation and an exponent.
The 2 largest studies to date included 262 and 183 patients.
The 2 largest studies to date included 26 patients2 and 18 patients.3
The largest lesion found in the first study was 10 cm.2
The largest lesion found in the first study2 was 10 cm.
When a multiple citation involves sufficient superscript characters to create the appearance of a “hole” in the print copy (20-25 characters, including spaces and punctuation, depending on the column width and type size), use an asterisk in the text and give the citation in a footnote at the bottom of the page (Figure).
Note: (1) Reference numerals in such a footnote are set full size and on the line rather than as superscripts. (2) The spacing is different from that in superscript reference citations. (3) If 2 or more such bottom-of-the-page footnotes appear in a single article, use an asterisk for the first footnote, a dagger for the second such footnote, a double dagger for the third. Note: This is less relevant for the Web.
As reported previously,*
*References 3, 5, 7, 9, 11, 13, 21, 24-29, 31.
Note: In tables, if a cell in the table involves citation of a reference number and a footnote symbol, give the reference number first, followed by a comma and the footnote symbol (eg, 3,a) (see 4.1.3, Visual Presentation of Data, Tables, Table Components).
If the author wishes to cite different page numbers from a single reference source at different places in the text, the page numbers are included in the superscript citation and the source appears only once in the list of references. Note that the superscript may include more than 1 page number, citation of more than 1 reference, or both, and that all spaces are closed up.
These patients showed no sign of protective sphincteric adduction.3(p21),9
Westman5(pp3,5),9 reported 8 cases in which vomiting occurred.
In listed references, do not use ibid or op cit.