Citing something you read somewhere else is called a “secondary citation.” We really recommend you try everything else before doing this. Why? You want to make sure that an author has interpreted the source correctly. Basically, people are people and you want to make sure that haven’t made a mistake.
What this means is you should definitely try to find the original source yourself. If it’s a book, check the Shared Library Catalogue to see if Western or the affiliate libraries have a copy. Failing that, you can try London Public Library (if you have a London address you can get a library card for LPL. Otherwise you can use their books inside their libraries). Your third option for books would be to check Google Books: they don’t have every book, and they definitely don’t have every page, but it’s worth a shot.
If you still can’t find it, talk to your professor or a library staff person. Your prof might be okay if you just cite the abstract, for example, but you need to ask them. The library can help you with the Interlibrary Loan process, where we borrow material from other university libraries. This process often takes time, though (i.e. 1 week for articles), so it isn’t always an option.
If you end up having to do a secondary citation, most citation styles have an example for this. APA, for example, requires that you include both the primary and the secondary citations in the body of your paper. I found a good example of this from the Online Writing Lab at Purdue University:
“Give the secondary source in the references list; in the text, name the original work, and give a citation for the secondary source. For example, if Seidenberg and McClelland’s work is cited in Coltheart et al. and you did not read the original work, list the Coltheart et al. reference in the References. In the text, use the following citation:
Coltheart, M., Curtis, B., Atkins, P., & Haller, M. (1993). Models of reading aloud: Dual-route and parallel-distributed-processing approaches. Psychological Review, 100, 589-608.”
— OWL at Purdue, APA Formatting and Style Guide: Reference List: Other Print Sources, Accessed November 15, 2010 from: http://owl.english.purdue.edu/owl/resource/560/09/.
Check the Brescia citation guides for examples on how to cite a secondary citation – but always check with your prof before including them in your final paper!