Web of Science includes the Science Citation Index, Social Sciences Citation Index, and Arts & Humanities Citation Index. The databases search "current and retrospective multidisciplinary information from approximately 8,500 of the most prestigious, high impact research journals in the world."
Cited reference searching allows users to "navigate forward, backward, and through the literature, searching all disciplines and time spans to uncover all the information relevant to their research." Citation indexes allow the user to track a particular article to see if it has been cited by other authors and discover more recent articles that may be crucial to your research.
To trace citations using Google Scholar, click on the "cited by" link. This is a good supplemenent to the Social Sciences Citation index.