Search for more e-books through these databases:
Remember it's important to evaluate your sources before using them for research. Evaluation criteria includes: relevancy, accuracy, authority, currency, and purpose. You can learn more at this website about evaluating web sources developed by UC Berkeley Library.
Here are a couple reference books which may be useful. Search for more using the catalog! (To narrow your search in Primo specifically to reference books, once you've entered your search, under the "Material Type" drop-down menu on the left side of the screen, limit to "Reference Entries" and "Books/Ebooks").