As you are starting to explore a new research topic, reference sources are a good way to gain background information on your topic. High quality, academic, multivolume sets, will often give you the beginnings of scholarly research on a subject by providing a short bibliography of important works on the subject.
Even with advanced subject knowledge of an area, you will run across unfamiliar people, places and events. Library reference sources will allow you to quickly fill in those gaps and improve your contextual knowledge with more reliability than a Wikipedia article.
Credo is an online fullt text database of over 400 reference sources. You can search them all together to bring up a variety of articles related to a topic.