UTL SUBJECT & RESEARCH GUIDES can provide subject-specific library resources to help you get started.
They include lists of REFERNCE SOURCES, ARTICLE DATABASES, and ways to search for BOOKS. For example:
Interdisciplinary Subject Guide
History Subject Guide - Robarts Library
HPS 319 Research Guide - History of Medicine II: 17th - 20th Century Resources
History Research Guide - Robarts Library
HIS 109 Research Guide - The Development of European Civilization from 1350-1945