Referencing - that is, citing all the sources you have consulted for your assignment - is an extremely important part of your work. This is not only to protect yourself against charges of plagiarism (passing off other people's work as your own), it also enables a reader to check your sources without difficulty.

In Earth Science, we use the referencing style of the journal Geology:

http://www.geosociety.org/pubs/geoguid.htm

and as fourth year students have to produce a paper in this style, it is as well to get used to it early. This style is also known as an 'author/date system', reflecting how your reference should appear within the text itself.

Two types of referencing are required in the author/date system:

embedded references in the text; and
a list of all references cited (sometimes called a bibliography) on a separate page attached to the text

Every essay and assignment needs both embedded references and a references cited page.

Embedded References and Corresponding Entries on References Cited Page

Embedded references:
In the text, in round brackets, put either the author's last name and date of publication, or the website number that corresponds to the full url and access date to be found on the references cited (or bibliography) page:

Single author: The Modern fauna also had to develop more effective survival techniques (Harper, 2006).
Multiple authors: This development is no longer speculative, but fact (Schopf et al,. 2002).
Multiple references: No evidence was found of intelligent design (Darwin, 1998; Ridley, 2003, Futuyama, 2005; Barton et al. 2007).
Website: Brachiopod-dominated assemblages fall into a number of ecogroups (website 1).

Corresponding entries on the references cited, or bibliography page would be:

Barton, N.H., Briggs, D.E.G., Eisen, J.A., Goldstein, D.B. and Patel, N. H., 2007, Evolution, New York, Cold Spring Harbor Laboratory Press, 833 p.

Darwin, C.R., 1998, On the Origin of Species by Means of Natural Selection, London, Wordsworth Editions Ltd. 416 p.

Futuyama, D., 2005, Evolution, Sunderland M.A., Sinauer, 545 p.

Harper, E.M., 2006, Dissecting post-Palaeozoic arms races. Palaeogeography, Palaeoclimatology, Palaeocology, v. 232, p.322-34.

Ridley, M., 2003, Evolution, London, John Wiley & Sons, 792 p.

Schopf, J.W., Kudryavtseve, A. B., Agresti, D. G., Wdowiak, R. J. and Czaja, A. D., 2002, Laser-Raman imagery of Earth's earliest fossils, Nature, v. 416, p.73-76

Website 1: http:\\www.fossils-facts-and-findscom/brachiopods.html (19 December 2009)

Explanation of references cited

Books: information required, all without italics, inverted commas, or, as a rule, brackets:

name(s) of author(s) (books should be listed alphabetically, by author surname)
if more than 1 author, list them all in the order they appear in the book
similarly if there are editor(s) instead of author(s)
date of publication
name of book
city of publication
publishing house
total number of pages in book

Journals: information required, all without italics, inverted commas, or, as a rule, brackets:

name(s) of author(s) listed alphabetically, by author surname)
if more than 1 author, list them all in the order they are attached to the article
similarly if there are editor(s) instead of author(s)
date of publication
full name of article
full name of journal
volume number
inclusive page numbers of the article

Websites: put in whole url line and, in brackets, the date accessed.

CDs: put in the information as for a book or journal, but add CD ROM at the end.

Quoting from a thesis:

name and initial of author
year of thesis submission
title of the thesis
name of university to which the author is/was attached

Other information about references:

Multiple references in a sentence:
References normally come at the end of a sentence, before the full stop. If, however, you have more than one reference in a sentence, put the first reference next to its subject. For example:

A mid ocean ridge is formed by the separation of two oceanic plates, when the sea floor spreads (Marshak, 2005) and the oceanic ridges all together extend for a total distance of over 40,000 kilometers (Farris et al., 2003).

Quoting a source verbatim:
If, for some reason, you absolutely HAVE to quote from a source verbatim, you need to put the page number after the year in your embedded reference. For example:

It was what has been called Bacon's 'restless curiosity' that drove him to his death (Benton and Harper, 2009, p. 4).

This is the only circumstance in which a page number should appear in a text. A specific page number never appears in on References Cited or Bibliography page.

Figure/graph/diagram numbers are usually enclosed in square brackets and it's fine if they appear next to the reference, if that is appropriate for the text:

80% of the world's active volcanoes are found at convergent boundaries (subduction zones); another 15% where plates separate; and the remaining 5% within the plate interiors [Fig. 1] (Press et al., 2004).

Figures can be placed after the text which refers to them, or attached to the essay on separate pages:

Appendices: Appendices, for example:

Appendix 1: sample descriptions

should be placed at the end of the text, before the bibliography or references cited.

For more information and examples: http://www.geosociety.org/pubs/geoguid.htm

Remember: the point of referencing is that your reader should, quickly and easily, be able to locate your source. If you find a source that you're not sure how to reference, use your head and BE CONSISTENT.