It's possible that someone already has started your research for you! Bibliographies and overviews summarize the research on a topic and provide citations to the books, articles, and other resources that the author recommends as most important. If you find a bibliography or overview on your topic, you can then track down those books and articles to determine whether they're useful to you.
These resources will help you find e-books and print held by Notre Dame, other local libraries, or books held at other libraries worldwide.
Below are some additional databases for searching the literature in fields with which Peace Studies has joint doctoral programs. Additional database suggestions are available here.