(These techniques will work in both the library catalog and WorldCat.)
To search systematically for books on a particular topic, it can be useful to search the standardized library subject for that topic. Sometimes the library subjects are not intuitive, sometimes they are. There will likely be more than one subject term that you'll need to look at for your topic -- both ethnicity and race, perhaps. You can use either the basic or the advanced search options to search for subjects, use the pull-down menu to select "subject."
Below are examples of Library of Congress Subject Headings for some topics related to this course. Click to view books held in the University of Chicago Library on these subjects.