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.
Encyclopedia of Graphic Communications by 
The Museum of Broadcast Communications encyclopedia of radio by 
Encyclopedia of Television by 
Language and communication: a cross-cultural encyclopedia by 
Encyclopedia of new media: an essential reference to communication and technology by 
The Advertising Age Encyclopedia of Advertising by 
Encyclopedia of Wireless Telecommunications by 
Encyclopedia of rhetoric and composition: communication from ancient times to the information age by Remember, reference sources are only FYI!
Never cite a reference source in your research paper or project.
You can use a reference source to lead you to other academic sources, however, by finding the citations provided in the References/Bibliography/Works Cited list.
