"Use reference books, also called reference or background sources, to get quick specific facts or information or an overview of a subject...Some examples of reference sources are: dictionaries, encyclopedias, bibliographies, almanacs, directories, atlases, and handbooks. These can be online or in print" ["What are reference books (or reference sources)?", Simon Fraser University Library].
Reference sources can also point to scholarly sources in their list of references or suggested resources for further reading.