The following is based on Section 5.7.13 (204) of the MLA Handbook describes on how to cite A Letter, a Memo, or an E-mail message:
"Treat a published letter like a work in a collection (see 5.5.6)....Treat memos similarly: give the name of the writer of the memo, a description of the memo that includes the recipient, the date of the document...." (MLA 157)
Following general MLA principles, a citation to a document within the Foreign Relations of the United States, could be formatted like this:
Johnson, Louis. "Memorandum From Secretary of Defense Johnson to the Secretary of the Army, The Secretary of the Navy, and The Secretary of the Air Force regarding Support of Covert Operations of CIA." 19 January 1950. Document 1 of Foreign Relations of the United States, 1950-1955: The Intelligence Community. Washington: Government Printing Office, p. 1-2. Print.
For FRUS documents found online, "Instead of concluding with Print as the medium of publication, record the following information in sequence:
1. Title of the database or Web site (italicized)
2. Medium of publications consulted (Web)
3. Date of access (day, month, and year) "
(MLA Handbook 187)
Johnson, Louis. "Memorandum From Secretary of Defense Johnson to the Secretary of the Army, The Secretary of the Navy, and The Secretary of the Air Force regarding Support of Covert Operations of CIA." 19 January 1950. Document 1 of Foreign Relations of the United States, 1950-1955. United States. Dept. of State. Washington: Government Printing Office, p. 1-2. U.S. Department of State, Office of the Historian. Web. 30 April 2012.
Declassified documents from other sources:
Helms/Kissinger, September 12, 1970, 12:00 noon. TELCON. (Sanitized transcript of telephone conversation concerning the Allende administration in Chile). Posted September 10, 2008. National Security Archive Electronic Briefing Book No. 255. Web. 1 May 2012.
MLA Style -- References in the body of the paper
MLA documentation style uses brief parenthetical citations in the text that lead to the list of works cited. To cite government documents in parenthetical references, the MLA Handbook refers users to page 224, Section 6.4.5. Citing a Work by a Corporate Author.
Following MLA Style guidelines, the first element in a parenthetical reference (generally, the author) should correspond to the first element in the List of Works Cited.
If you are referencing a number of legislative documents, you will need to include enough information in the parenthetical reference to direct the reader to the correct reference in the List of Works Cited.
"When giving the name of a corporate author in parentheses, shorten terms that are commonly abbreviated...." (MLA Handbook 224) e.g., (U.S. Cong. House. Comm. on House Administration).
As you can see, even with the abbreviations, this makes for a fairly long reference and may make your paper more difficult to read. One alternative is to include the reference in a sentence.
"In 2001, the United States Congressional Committee on House Administration published their report on the Bipartisan Campaign Reform Act of 2001 (House Rept. 131). In the report, ..."
If you need to reference a number of legislative or legal documents throughout the body of your paper, you may wish to use another citation style, such as the Chicago numbered note style or APA style. You will need to choose the citation style that best fits your needs (and approved by your instructor) and use it consistently throughout the paper.