Reference works are fantastic resources at any stage of your research. Consult them when you have a topic idea, as they will give a concise overview of your topic, including key figures, terms, and concepts. Return to them midway through your research to help you identify (and begin to research) any gaps you may have. Many reference books are written by experts and offer not only information but also excellent bibliographies for further research. Use these bibliographies to track down other related sources.