As Dr. Adam Wood mentions in the Think About Your Topic section of the guide, "Searching in the secondary literature will help you identify the relevant primary works and what sections to focus on." He goes on to direct you to the resources below, all of which are included on the Recommended Resources tab.
In addition, consider searching Google Scholar (see below). Scholar allows one to search across the entire full text of the books and articles that is indexes, which goes further than most other resources to uncover relevant conversations on your topic.
While examining your search results, be on the lookout for hyperlinked terms and phrases that can direct you to other possible search terms and, by clicking on them, provide a new set of results to explore.
Immediately below is a video tutorial of using PhilPapers, considered the premier database for secondary literature in philosophy. A good place to start with a well developed subject hierarchy to help you drill down to your specific topic.
In addition to the Stanford Encyclopedia, PhilPapers and Philosopher's Index, Google Scholar is a great way to find scholarly articles or book citations. After searching, look for features in your results that can help you find related articles:
Linking Google Scholar to Buswell's collection can help you find your results more efficiently. The PDF below shows you how to link Google Scholar to Buswell Library so you can check if we have access to a resource.