University of Birmingham Computer Science

A Referencing Style Guide

Peter Coxhead


  1. Introduction
  2. References in the text (citations)
  3. List of references
  4. Referencing online sources
  5. Footnotes
  6. See also

1 Introduction

Correct and consistent use of a standard referencing convention is essential in producing a report, thesis or paper. One version of what is often called the "Harvard system" is briefly explained below. Different authors (and different journals) use variants of the basic system; what matters most is consistency.

This is not a guide to avoiding plagiarism, but proper referencing is one of the main ways for students to avoid being accused of cheating through improperly copying other people's work. So learn to reference fully and properly!

Referencing a source involves two separate steps:

In the Harvard system:

2 References in the text (citations)

There are two ways to include a reference in the text.

  1. If the reference name naturally forms part of a sentence, then include it exactly as if no reference is being given. Follow the name by a space and the full year of publication, enclosed in parentheses. (Multiple authorship is dealt with in the same way.) Examples:

    * Carson (1970) argued that ...
    * The system developed by Brown & Smith (1986) is ...
    * The declaration of human rights published by the United Nations (1948) was ...
    * AI has been effective as Hamza (1983) claims ...
    * On the other hand, Jones et al. (1988) have reported that ...
    * Carson's (1970) paper argues ...

    The last example is not universally acceptable; the possessive can always be avoided by appropriate re-phrasing, e.g.:

    * A paper by Carson (1970) argues ...

    If the parenthesized year is crossed out, the remaining sentence, including punctuation, must still be correct. Thus the following are wrong:

    X An earlier paper Carson (1970) states that ...
    X It has been claimed that in this area AI has been effective, Hamza (1983).

    Multiple references by the same author(s) can be dealt with by placing a list of years in parentheses. Examples:

    * Jones (1980, 1983, 1987) has repeatedly argued that ...
    * The system developed by Brown & Smith (1986, 1988) is ...

  2. If the reference name does not form a natural part of the sentence, include both the name and the year, enclosed in parentheses, at an appropriate point in the sentence. (A comma can be placed between the name and the year, but this must be done consistently.) Examples:

    * An earlier paper (Carson 1970) argues that ...
    * The ARGA program (Brown & Smith 1986) is ...
    * It has been claimed that AI is effective (Hamza 1983) ...
    * The Universal Declaration of Human Rights (United Nations 1948) specified ...
    * On the other hand, it has been reported (Jones et al. 1983) that ..

    If the parenthesized name and year are crossed out, the remaining sentence, including punctuation, must still be correct. Thus the following are wrong:

    X An earlier paper by (Carson 1970) argues that ...
    X As claimed in (Hamza 1983), ...

    In the style of referencing in which formats such as [Hamza83] are used, it would be correct to write something like "As claimed in [Hamza83], ...". In the Harvard style, it is not. Don't mix up the two styles. If you decide to use the Harvard style, use it consistently.

    Multiple references can be placed in a single list, using semi-colons to separate different authors:

    * This point has been made a number of times (Jones 1980, 1983a, 1987; Brown & Smith 1986; Carson 1970), but ...

Note the following points:

For some further notes on referencing online material, see Section 4 below.

3 List of references

There is a distinction between 'References' and 'Bibliography'. References are those sources actually referred to in the text. If the reference "Jones (1980)" occurs in the text, there must be a full description of it in the list of references. Short of blatant plagiarism, there are few more serious academic sins than the floating reference! If there is also a bibliography, then it lists those sources which were consulted and found relevant, but are not actually referred to by name in the text. If you use a combined bibliography and list of references (not ideal), make sure this is clear to the reader.

A single list of references should be given at the end of the thesis or paper – never one per chapter. The list must be ordered by name, then year. For this reason the year is usually placed immediately after the name, as it makes ordering simpler (although putting the year last is also logical and conforms more closely to library cataloguing systems). Multiple authors, however many there are, must never be reduced to "et al." in the list of references, even though they were in the body of the text.

It is not easy to give an exhaustive list of the possible formats for a full reference; variation in style is common, but the twin goals must always be completeness and consistency. 'Completeness' means that from the reference alone (i.e. with no other knowledge of the subject), the reader can locate the original source or obtain a copy. Some examples are given below. (Online material is discussed separately in Section 4 below.)

Referencing online material is discussed in the next section.

4 Referencing online sources

Traditional referencing systems were developed for paper-based sources. Adapting them to online sources can sometimes be a problem.

Some documents appear both in printed form and on the web, in which case the printed form should treated as primary, although the URL can usefully be given as additional information in the list of references, for example by adding a note of the form "[online at URL, accessed FULL_DATE]".

Where a work is only published on the web, if the author and date of 'publication' can be found (e.g. from the document itself or by using commands like 'Page Info' in Firefox), then the author's name and the date can be used as a reference in the text in the normal way. For example, using this document as the source:

* Coxhead (2009) states that ...

The entry in the list of references should give a title for the document (e.g. the title of the web page) together with the URL and the full date on which the URL was accessed. This latter is particularly important since online material is transient; the date of last access gives some indication of the likelihood of the information still being at the quoted URL. For example, this document could be referenced as:

* Coxhead, P. (2009), "A Referencing Style Guide", [accessed 17 Oct 2009].

Since a University department is a clearly defined entity, it could also be treated as the 'publisher' and a more conventional style format used:

* Coxhead, P. (2009), "A Referencing Style Guide", School of Computer Science, University of Birmingham, Birmingham B15 2TT, UK [online at, accessed 17 Oct 2009].

With web pages, it is often necessary to use the name of an organization instead of the name of the author (e.g. "Sun Microsystems (2007c)").

Wikipedia is not a primary source (although often a good provider of references to original sources). Wikipedia articles are mainly useful as overviews; see, for example:

* Wikipedia (2013), "Parenthetical referencing", [accessed 5 Jul 2013].

Finding a date of 'publication' can be a problem, since dates given in the document are sometimes not up-to-date, and 'Page Info' commands will simply return today's date for web pages generated dynamically by the server. One possibility is to use the date on which the URL was last visited; this at least gives some information to the reader. In the last resort "n.d." (for "no date") can be used.

Where information needed to construct a proper reference is simply not available, it may be better to give up, and just include the URL in the text or as a footnote.

5 Footnotes

1. In the original Latin usage, et alii would have been used where the people in question were all men or were a mixture of men and women, and et aliae where they were all female. The gender neutral term et alia is now preferred by many, in spite of the purist argument that it means "and other things" not "and other people". The abbreviation avoids engaging with this issue. Return to main text

6 See also