The U.S. Government produces massive amounts of information. Here are two guides to using government publications for historical research, by Government Information librarian, Sanga Sung.
Foreign Relations of the United States, commonly referred to as FRUS, prepared and issued by the Department of State since 1861, is a compilation of selected documents from the files of the Department of State, the White House, and other agencies. It presents a historical view of American foreign policy and now comprises more than 450 individual volumes. Besides providing the text of important foreign policy documents, FRUS also includes source citations (printed either with the document or as footnotes) that indicate the location of the original documents. In this way, FRUS serves as a guide to the location of additional documents on the same and related subjects not selected for publication.
There are several ways to access FRUS:
Research guides (from other libraries) to government information relating to the US war in Vietnam. Note that some links from these guides lead to subscription-based sources. You will not be able to use these links, but you should check our Library's A-Z List of resources, and our library catalog, to see if we have access to the sources (we probably do).