(1968). United States government correspondence manual. U.S. Government Printing Office.
Cita Chicago (17th ed.)United States Government Correspondence Manual. Washington: U.S. Government Printing Office, 1968.
Cita MLA (9th ed.)United States Government Correspondence Manual. U.S. Government Printing Office, 1968.
Atenció: Aquestes cites poden no estar 100% correctes.