CBE number system Though scientific publications document sources in similar ways, the details of presenting source information vary from journal to journal. Often publications provide prospective authors with style sheets that outline formats for presenting sources. Before submitting an article to a scientific publication, you should request its style sheet. If one is not available, examine a copy of the publication to see how sources are listed. When writing for a science course, check with your instructor about which format to use. Biologists, zoologists, earth scientists, geneticists, and other scientists may use an author-date system of documentation (one type of author-date system is shown in the APA documentation section of this booklet). Or they may use a number system in which each source is given a number in the text. Following the text, full publication information for each numbered source is provided in a list of references. Entries in this list are given in the order in which they are mentioned in the paper. One type of number system is outlined in Scientific Style and Format, published by the Council of Biology Editors (6th ed., 1994). In the paper, the source is referenced by a superscript number: IN-TEXT CITATION Scientists are beginning to question the validity of linking genes to a number of human traits and disorders1. At the end of the paper, on a page titled "References" or "Cited References," the source is fully identified according to CBE style. ENTRY IN THE REFERENCE LIST 1 Horgan J. Eugenics revisited. Sci Am 1993; 268:122–31. The number format for citing sources is less cumbersome and distracting than the author-date method, especially when you need to refer to many works one after another in the text of your paper. However, it is much less informative for the reader. If the author or publication date of a particular work is important to your discussion, you must add this information to the sentence. Smith11, studying three species of tree frogs in South Carolina, was the first to observe. . . . This species was not listed in early floras of New York; however, in 1985 it was reported in a botanical survey of Chenango County13. As in the author-date format, if you need to refer to specific portions of a source, make this clear in the citation. Some writers also include the page number for a direct quotation. My data thus differ markedly from Markam's study on the same species in New York5 (Figs 2,7). "Tailbeating" behavior, as defined by Cheevers and Briggs3(p 25) is. . . .