Faculty members carefully their textbooks, which are often structured to be guides to a discipline. See what your textbook can offer you as a starting point for your research beyond the course readings.
Once you have citations to track down, search for the titles on the Penn Libraries homepage, and select the appropriate item from the resulting screen. Article citations should appear in the Articles+ column of results; book citations should appear in the Catalog column.
Use dictionaries, encyclopedias, and handbooks to learn quickly about the state of research on your topic. A good encyclopedia article should describe major themes, current research fronts, and controversial areas; it should also provide a brief bibliography of classic, important, or definitive works on your topic. Handbooks generally offer chapters on specific aspects of a topic: together, the handbook's chapters should provide a broad overview of the state of research; individually, chapters may be narrowly focused.
Corsini, AccessMedicine, DSM-5. Choose the one most suitable for your topic, but expect to look at another one, just in case. Expect brief articles with one or two paragraphs, with citations to the classic experiment or a recent literature review.
Handbooks. Read for a broader context. Expect long articles, with a historical perspective and lots of citations to important research.
You're searching for a phrase or a couple words. How effective can relevance ranking be for that kind of search? Do your search, look at all likely results. Use your browser's "Find" tool.