How can I find out who cited an author's work?

You have several tools available that can help you with this. The best may be the database Web of Science's 'Cited Reference Search' tool, but ScienceDirect, Google Scholar, Google Books (search citation in books' full-text there), and Amazon's Search Inside search will also be helpful in finding all relevant, cited articles. Those are all multidisciplinary sources, but Belk Library also has access to a number of more discipline-specific cited reference tools as well, many in our EBSCO databases (PsycINFO, Business Source Premier, Communication & Mass Media Complete, etc.), some in our Proquest Databases (Socialogical Abstracts & more), and in a few other places too: MathSciNet and SciFinder Scholar. For more information, this guide is very helpful: http://www.bc.edu/libraries/help/howdoi/howto/pubcitation.html