Manuscripts and Archives Division, The New York Public Library. "Marsha P. Johnson hands out flyers for support of gay students at N.Y.U." The New York Public Library Digital Collections. 1970. http://digitalcollections.nypl.org/items/510d47e3-57b0-a3d9-e040-e00a18064a99
Encyclopedias and other reference resources are excellent places to start contextualizing primary sources.
Subject encyclopedias, handbooks and overviews are scholarly, tertiary works written by experts on a variety of topics. The articles are typically longer and more detailed than those found in general encyclopedias. You usually can expect to find the following important information in articles in subject encyclopedias:
Start with these subject encyclopedias and branch out as needed.
Print encyclopedias and dictionaries are located on the first floor of Collins Library.