Style Issues: et al., op cit. and ibid.

These three Latin abbreviations are much misused, and it is probably preferable to avoid using them most of the time. However, there are occasions within the Harvard system when they are useful.

Et al.

This is an abbreviation for et alii which means 'and others'. It is standard practice today in referencing to name every author in a full reference, though if there are more than three authors, the extra names can be represented by 'et al.' (although in specific subjects this might vary).

However, a long sequence of names would be clumsy if used within an in-text citation, so for three authors or more, the form (first author et al., date) is normally used, e.g. (Fry et al., 1999).

Where there are only two authors, both are always cited.

Op. cit.

This is an abbreviation for the Latin opere citato which means 'in the work cited'. This should only ever be used in a full reference when the work concerned has itself a full reference to it (that is, not within another reference).

For example, if making use of several chapters from an edited book, or papers from a single journal edition, it is usually simpler to give the book or journal a reference:

Fry, H., Ketteridge, S. & Marshall, S. (eds.), 2003, A Handbook for Teaching and Learning in Higher Education, second edition. London: RoutledgeFalmer.

Then all references to chapters/papers in it can take the form:

Wakeford, R., 2003, Principles of student assessment. In Fry et al., (2003), op. cit., pp. 42 - 61.

But if only a single chapter is used, the reference should take this form:

Wakeford, R., 2003, Principles of student assessment.In Fry, H., Ketteridge, S. & Marshall, S.(eds.), 2003, A Handbook for Teaching and Learning in Higher Education, 2nd Ed. London: RoutledgeFalmer, pp. 42 – 61

You can see that if two chapters are used it will be more economical to reference the volume directly and use op cit for each chapter reference. There is no case for using op. cit. in a standard in-text citation, however. In fact op. cit. can even be omitted from the references above, because the fact that an abbreviated reference is given should refer the reader to the full item placed alphabetically elsewhere in the list of references.


This is an abbreviation for the Latin ibidem meaning 'in the same place'. In referencing it means 'in the same source'. There is no case for using ibid. in a full reference in the Harvard system (as opposed to the numeric system). There are occasions when it is useful, and helpful to the reader, to use it in in-text citations. If making several references to a particular source in succession, with no other reference intervening, then ibid. can be used.

For example:

Russell (1961, p. 122) claims that Plato was influenced by Pythagoras and Socrates in particular. Their influence on Plato's most important dialogue, the Republic, will become evident in the following discussion of this work.

Much of the Republic is made up of debate between real philosophers from the past, including Socrates, who generally supports Plato's views. Russell comments, "Plato's Republic, unlike modern Utopias, was perhaps intended to be founded ... The rule of philosophers had been attempted by Pythagoras..." (ibid., p.134)

Unfortunately for Plato's utopian ambitions, he was living in Syracuse, which was at war with Carthage, and "in such an atmosphere, no philosopher could have achieved much." (ibid., p. 134)