Referencing

Why reference?

Scientific writing should always be referenced. This is so that a reader can locate related work, to give due credit to previous scientific work, and to avoid accusations of plagiarism.

References are specifically referred to in the text and differ from a bibliography, which is a collection of relevant sources. There are many different styles of referencing, but the two that are in common use for physics are the Harvard system and the numerical indexing system. The sections below are adapted from the IoP guidelines External link icon for authors. The i-cite webpages give additional information on referencing, including referencing software.

Harvard system

A summary sheet about the use of the Harvard system is available here (pdf, 99 kB), and a more detailed guide is available here (pdf, 77 kB).

In the Harvard system, the name of the author appears in the text with the year of publication. Where there are two names, both are given in the text. Where there are more than two authors only the first is listed in the text with the others indicated by et al, but all the authors are listed in the references at the end. If the same author (or group of authors) publishes in the same year, then the first reference has the suffix a, the second b, etc. The reference list at the end of the paper is in author surname and year order.

An example would be:

The original work (Weisbuch and Vinter 1991) has now been questioned by Bauer (1992) and Adler et al (1994a, b) who find that ...

References
Adler, F.J., Kocevar, P., Schilp, J., Kuhn, T. and Rossi, F. (1994a) Coherent and incoherent charge carrier response in the femtosecond spectroscopy of semiconductors, Semicond. Sci. Technol., 9, 446 - 8.
Adler, F.J., Kuras, G.F. and Kocevar, P. (1994b) Carrier-carrier scattering versus coherence in high semiconductors SPIE Proc, 2142, in press.
Bauer, G.E.W. (1992) Optics of Excitons in Confined Systems (Inst. Phys. Conf. Ser. 123), ed. A. D'Andrea et al (Bristol: Institute of Physics), P283.
Weisbuch, C. and Vinter, B. (1991) Quantum Semiconductor Structures (San Diego: Academic), P124.

Numerical System

In this system references are numbered sequentially through the text. The numbers are shown either in square brackets or as superscripts, and one number can refer to more than one reference.

The Harvard example above, rewritten for the numerical system, would be:

The original work [1] has now been questioned by Bauer [2] and Adler et al [3] who find that ...

References
[1] Weisbuch, C. and Vinter, B. (1991) Quantum Semiconductor Structures (San Diego: Academic), P124.
[2] Bauer, G.E.W. (1992) Optics of Excitons in Confined Systems (Inst. Phys. Conf. Ser. 123), ed. A. D'Andrea et al (Bristol: Institute of Physics), P283.
[3] Adler, F.J., Kocevar, P., Schilp, J., Kuhn, T. and Rossi, F. (1994a) Coherent and incoherent charge carrier response in the femtosecond spectroscopy of semiconductors, Semicond. Sci. Technol., 9, 446 - 8.
Adler, F.J., Kuras, G.F. and Kocevar, P. (1994b) Carrier-carrier scattering versus coherence in high semiconductors SPIE Proc, 2142, in press.

Referencing electronic sources

A lot of information is available electronically via the internet. Such information has not normally been through scientific peer review, and as a result may be unreliable i.e. untested or wrong. We can still use this material with care but we need to reference it to avoid being accused of plagiarism External link icon. Useful advice is given here External link icon, and this site (Bedford St. Martin's College) gives examples of references in the Chicago style External link icon. This involves putting the URL in angle brackets and recording the date when the site was visited (since links can be moved). The reference should include:

  • the author's name,
  • the full title of the document in quotation marks,
  • the title of the complete work in italics,
  • the date of publication or last revision,
  • the full web address (URL) enclosed within angle brackets exactly as entered in the web browser i.e. preserving any capital letters, and
  • the date of the visit in brackets.

Some examples are:
Burka, Lauren P. "A Hypertext History of Multi-User Dimensions." MUD History. 1993. <http://www.ccs.neu.edu/home/1pb/mud-history.html> (5 Dec 1994)
WMAP Project. "What is inflation theory?" Cosmology: the study of the universe 30 Apr. 2004. <http://map.gsfc.nasa.gov/m_un/uni_101inflation.html> (1 Oct. 2004)

Further examples

Examples of scientific essays and papers using different referencing systems (and also showing various other features of scientific writing such as figure captioning, use of equations, etc.) are available below, and originally came from the Los Alamos physics e-print archives.

Nature paper on redshift radio galaxies using the numerical system (pdf, 401 kB).
Conference paper on galaxy formation using the numerical system (pdf, 122 kB).
Essay on quantum physics using the Harvard system (pdf, 144 kB).
Essay on quantum gravity using the numerical system (pdf, 125 kB).