All authors should be included in reference lists unless there are more than five, in which case only the first author should be given, followed by ‘et al.’. Authors should be listed last name first, followed by a comma and initials of given names. Titles of cited articles are required for Articles, Perspectives and Reviews, but not for Commentaries, Brief Communications or News and Views. Titles of articles should be in Roman text and titles of books in italics; the first word of the title is capitalized, the title written exactly as it appears in the work cited, ending with a period. Journal names are italicized and abbreviated (with periods) according to common usage; refer to Index Medicus for details. Volume numbers appear in bold. For book citations, the publisher and city of publication are required (e.g., John Wiley & Sons, Hoboken, New Jersey, USA, 2003).