"Use reference books (also called reference or background sources / resources) 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." (McKenzie, 2017).
Reference sources can also point to scholarly sources in their list of references or suggested resources for further reading.
Macmillan Encyclopedia of Marriage and Family by 
Parenting: Styles and Strategies by 
Principles of Sociology: Personal Relationships and Behavior by