Pay special attention to Subject terms (usually hyperlinked) used in bibliographic records for more related books of the same subject.
For books we don't own, you can request them thru Interlibrary Loan.
Don't forget to browse library stacks for books didn't come up under your keyword search but are related to your topic(s). Pay close attention to the shelves where you found useful books.
Google Scholar is a web search engine of scholarly literature across many disciplines and sources, including books, abstracts and articles. It is a Google search for scholarly literature. Remeber to change Settings (from the top menu bar or the triangle drop down icon on the right) in Google Scholar to get the links to full-text articles Lucy Sribner Library provides appear on your Google Scholar search results.
ILL quick link: