Q. how do I cite a reference for Roget's International Thesaurus 3rd edition 1965

To cite an entry from a reference work such as a dictionary or thesaurus, use the APA rules and examples at section 7.02 of the guide. Here is a pattern that you can use for your reference:

Advocacy. (1965). In Roget's International Thesaurus (3d ed., pp. xxx-xxx). Place of publication: Publisher.

You will need to enter page numbers, place of publication and the publisher.