Citation style

Scholarly and technical publications use many different formats for citing previously published work in their articles.

A citation allows an interested reader to verify a statement made in the text, to see the source of data, to gain more statistical detail, or to explore the original context of a quoted passage. Often, the text is marked with a superscripted number just after the section to which the citation is most relevant, or at the end of the relevant paragraph, where there may be more that one source indicated.

The superscripted mark may be a numeral, a Roman numeral, or a letter. Alternatively, the main authors of the cited reference source plus a date, in parentheses as in (Smith, 1997) may be provided. Variants of this approach are (Jones, 1997a) if Jones is cited for more than one 1997 article, and (Smith and Jones, 2000), and Timorof et al. 1927). Et al. is for et alia, meaning 'and others' in Latin, and this is usually used if there are more than three authors.

With word processing programs now widely available, it is easy to develop automatically generated, correctly numbered citations in documents. With Mediawiki software used for Citizendium, for example, there are good tools for annotating text with citations and generating a master list of sources, usually near the end of the article as end-notes. In some publications, citations are provided as footnotes on each page.

Attention needs to be given to giving definitive information in the endnote or footnote that is made about the source. on the other hand, in hard-copy published articles there is a premium on space, and many scholarly publishers demand very compact citation notes. This is less important in electronic journals.

Precise attention to the format and consistency of citations and other bibliographic information is expected in professional quality manuscripts. It is, however, not uncommon for authors to submit manuscripts for publication with inconsistencies, errors and missing information.

Examples of citation styles

Here are three examples of citations from Proceedings of the National Academy of Sciences, USA, a very well respected scientific journal (often called just PNAS by scientists).

17. Lockhart, P. J., Steel, M. A., Hendy, M. D. & Penny, D. (1994) Mol. Biol. Evol. 11, 605-612

31. Syvanen, M. & Kado, C. I., eds. (1998) Horizontal Gene Transfer (Chapman & Hall, London).

32. Day, M. (1998) in Horizontal Gene Transfer, eds. Syvanen, M. & Kado, C. I. (Chapman & Hall, London), pp. 144-167.

Citation 17 is a journal citation but unfortunately for the reader PNAS USA does not provide the article's title. Note the volume number is given in bold text bold , followed by page numbers. 31 is a book and 32 a book chapter.

The following another PNAS USA citation of an article in the journal Molecular Biology and Evolution, published by Oxford Journals:

13. Lake, J. A. (1991) Mol. Biol. Evol. 8, 378-385

It is available on line as a pdf file

Here we will find, at last, an article title:

Letter to the Editor. The Order of Sequence Alignment Can Bias the Selection of Tree Topology. James A. Lake

In the text of Lake (1991), the citation style is like this: (Lake et al. 1984; Woese and Olsen 1986), and in the end-notes the citations are listed like this:

LITERATURE CITED

AUER, J., B. SPICKER, and A. BOCK. 1990. Nucleotide sequence of the gene for elongation

factor EF- 1 alpha for the extreme thermophilic archaebacterium Thermococcus celer. Nucleic

Acids Res. 18:3989.

BALDACCI, B., F. GUINET, J. TILLIT, G. ZACCAI, and A.-M. DE RECONDO. 1990. Functional

implications related to the gene structure of the elongation factor EF-Tu form Halobacterium

marismortui. Nucleic Acids Res. 18:507-511.

BROWN, W. M., E. M. PRAGER, A. WANG, and A. C. WILSON. 1982. Mitochondrial DNA

sequences of primates: tempo and mode of evolution. J. Mol. Evol. 18:225-239.

Note that article titles are provide in this publication, but the system for providing page numbers is different from PNAS USA, and in this publication author's names are capitalized.

In short, there are many different citation style variations used today in scholarly literature.

How can authors work out how to cite publications correctly

A guide for how to provide citation details is provided to prospective authors by the particular scholarly publication.

One accessible example is from the internet publication [http://journals.plos.org/plosbiology/guidelines.php Public Library of Science Biology] (PLoS Biology) which is an Open Access journal.

They give the following guidelines for submitted manuscripts:

"PLoS uses the numbered citation (citation-sequence) method. References are listed and numbered in the order that they appear in the text. In the text, citations should be indicated by the reference number in brackets. Multiple citations within a single set of brackets should be separated by commas. Where there are more than three sequential citations, they should be given as a range. Example: "...has been shown previously [1,4–6,22]." Make sure the parts of the manuscript are in the correct order for the relevant journal before ordering the citations. Figure captions and tables should be at the end of the manuscript.

Because all references will be linked electronically as much as possible to the papers they cite, proper formatting of the references is crucial. For all references, list the first five authors; add "et al." if there are additional authors. You can include a DOI number for the full-text article as an alternative to or in addition to traditional volume and page numbers. Please use the following style for the reference list:

Published Papers

1. Sanger F, Nicklen S, Coulson AR (1977) DNA sequencing with chain-terminating inhibitors. Proc Natl Acad Sci U S A 74: 5463–5467.

Accepted Papers

Same as above, but "In press" appears instead of the page numbers. Example: Adv Clin Path. In press.

Electronic Journal Articles

1. Loker WM (1996) "Campesinos" and the crisis of modernization in Latin America. Jour Pol Ecol 3. Available: http://www.library.arizona.edu/ej/jpe/volume_3/ascii-lokeriso.txt. Accessed 11 August 2006.

Books

1. Bates B (1992) Bargaining for life: A social history of tuberculosis. Philadelphia: University of Pennsylvania Press. 435 p.

Book Chapters

1. Hansen B (1991) New York City epidemics and history for the public. In: Harden VA, Risse GB, editors. AIDS and the historian. Bethesda: National Institutes of Health. pp. 21–28."

(End of direct quote from PLoS Biology)

Practice at Citizendium

This is a heading of a work in progress.