Encyclopedias, dictionaries, handbooks, and Wikipedia are all examples of reference sources.
These sources are good places to start your research. You can find definitions and a brief overview of your topic by consulting a reference book or website.
Criminal Justice in America: the Encyclopedia of Crime, Law Enforcement, Courts, and Corrections
The Criminal Law Handbook
Handbook of issues in criminal justice reform in the United States
The Palgrave Handbook of International Cybercrime and Cyberdeviance
SAGE Encyclopedia of Surveillance, Security, and Privacy
