A reference source is a source that will provide general background information on a topic, such as an encyclopedia, dictionary, or handbook.
You are required to use one source from Credo in your bibliography
Reference works are excellent place to start your research, and can give you give an overview of a subject that will help you pick a topic and focus your research.
But remember that reference sources cannot be used as scholarly sources. But they are still a very helpful place to begin your research.
CREDO is a growing online collection of reference resources, including dictionaries, encyclopedias, atlases, and handbooks, from leading publishers, many of which include images, audio and video clips.