If your topic is "The Mexican Revolution of 1910" and you have successfully reduced your topic to a manageable theme – "The Land Reform Program of Emiliano Zapata" – how do you know which sources of information about Zapata and about land reform in Mexico are the kind that your instructor expects you to use?

• Find a good encyclopedia, like the Encyclopedia Britannica or the Columbia Encyclopedia, and look up "Emiliano Zapata."
• After the article on Zapata (which you should read), there will be a list of sources about him. These books, articles, or documents are the kinds of sources that serious researchers use.
• A good rule to follow is that if the source you are using is a serious one, the other sources it refers you to will be serious also.
• If you are in doubt about the quality of a source, ask the reference librarian if it is the kind of source that serious researchers would use.