Reference Material in the form of subject dictionaries, encyclopedias, and handbooks typically provide background essays, definitions, broad overviews of various topics, or other pertinent facts. A collection like Sage eReference can be very helpful for this sort of information.
Handbook of Reading Research
Methods of Literacy Research
Educator's Guide to Texas School Law
International Encyclopedia of the Social & Behavioral Sciences
International Encyclopedia of the Social Sciences
Review of Research in Education