If you read an article or book which cites some information that you want to cite, for the full reference always refer to the source where you found the information, not the original source.
Sue reads an article by Alex Byrne in the Australian Library Journal in which he cites or refers to statements made by Tim O'Reilly on his website..Sue wants to refer to O'Reilly's statement in her assignment.
Sue would acknowledge O'Reilly in her text but her reference is to the source where she saw the information. Sue might write as her in-text reference:
(O'Reilly 2005 cited in Byrne 2008)
In her reference list Sue would write a reference for Byrne's article because that's where she sourced the information. The entry in her References would be:
Full Reference list
Byrne, A. (2008) 'Web 2.0 strategies in libraries and information services', The Australian Library Journal, 57(4), pp. 365-376.