Look for the sources used by authors in their articles and other publications. The sources may be cited in a bibliography or at the bottom of a table, or referred to in a more general sense in the text of the article. The sources may be online or in print; they may be free or available only for a fee.
To track down cited publications, use tools such as:
Books not available through Rod Library may be available through the Interlibrary Loan Service. Log on to this service, called ILLiaD, and provide details for the publications you would like to borrow.