Encyclopaedia or dictionary - no author listed for entry
If there is no author evident for the entry in the dictionary or encyclopaedia provide the nameof the dictionary or encyclopaedia in italics and the year it was published.  No entry is needed in the reference list.  Refer to Snooks (2002, p. 199).

In-Text:             The Macquarie Dictionary (1997) defines...

References:    No entry is needed in the reference list

Encyclopaedia article - author listed for entry
If an author for the entry is evident, treat the same way as for a chapter in an edited book.

In-Text:               (Lazarus 2001)

References:      Lazarus, AA 2001, ‘Multimodal therapy' in WE Craighead & CB Nemeroff (eds), The Corsini encyclopedia of
                             psychology and behavioural science, 3rd edn, Wiley, New York, vol. 3, pp. 993-4.

Encyclopaedia or dictionary electronic format - no author listed for entry
To indicate the dictionary or encyclopaedia is in electronic format add 'online' after the title.  Snooks (2002) does not provide guidance for this type of reference.

In-Text:               The Mosby's dictionary of medicine nursing and health professions online (2009) defines....

References:      No entry is needed in the reference list

Encyclopaedia or dictionary electronic format - author listed for entry

In-Text:               (Weatherall 2005)

References:        Weatherall, D 2005, ‘Thalassemia' in DN Cooper (ed.), Encyclopaedia of the human genome,
                               Wiley, Hoboken, NJ, viewed 8 February 2011, <http://www.credoreference.com/entry/wileyhg/thalassemias>.

If you cannot find an example for what you are looking for then use: Chapter 12 'Methods of citations' from Snooks (2002)