Use the Tripod catalog for your home institution to look for all books (print and digital) owned by your college as well as the print titles at the other two schools.
The following searches are a sampling of possibilities. To find materials on a topic, try doing a keyword search in the Tripod Catalog to find relevant materials and then use the subject headings assigned to those titles to find more books. Note that all these searches are in the Books+Media channel. In examples #1 and 4 below, using keywords (rather than subjects) will pick up results from chapter titles.
(queens OR queenship) AND (power OR rule*) [Any Field] AND history [Subject]
(art patronage spain) [Subject] AND ("16th century" OR "17th century")
("Education of princes" OR "Kings and rulers -- Duties") [Exact Subject] Sorted by newest titles first
"marie de' medici*" [Any Field] Sorted by newest titles first
** Try opening a search above and replace one of the topics with your research interest.
WorldCat is an important place to look for many materials not owned by the Tri-College Libraries. This combined library catalog contains more than 500 million records describing items owned by libraries around the world. Many of these items are available to you though interlibrary loan. Also note that older primary sources are sometimes listed in WorldCat with open access URLs. Look for the results grouped as Internet to find possible sources.