You can easily add to the search terms for greater specificity. For example, if you wanted to find all Level 3 materials that were published by Penguin, you could search this way:
Over 700 books have been transferred from the English Language Center to the DU Main Library. This makes it easier for users to check out materials any time they want. Although the books are not physically shelved in a single location, the library catalog can bring all the materials together for easy discovery. The pages (tabs) in this guide are arranged by English language proficiency level, and contain links to limit to either fiction or nonfiction.
Keep in mind that most of these search results have several pages to look through: