Reference resources in a college library are more advanced and subject-specific than those you might be used to. These encyclopedias, dictionaries, and handbooks help to thoroughly define a topic while providing specific terms and phrases professional writers use to talk about your topic. Additionally, these resources will often refer you to other reliable web sources or articles about the topic. As you go through these resources, pay careful attention to the causes and their effects that are discussed.
If you're not sure what to look for in these sources, I've given you a few examples along with the questions that you might be able to answer with a background source on the topic. The questions are in the description, and if you select "more..." it will tell you what the article has to say.