United States. Postmaster General. (1932). Cost ascertainment: Instruction letter U; record of revenues by classes on drop mails and station letter-box collections by Railway Mail Service. U.S. GPO.
Chicago Style (17th ed.) CitationUnited States. Postmaster General. Cost Ascertainment: Instruction Letter U; Record of Revenues by Classes on Drop Mails and Station Letter-box Collections by Railway Mail Service. Washington: U.S. GPO, 1932.
MLA (9th ed.) CitationUnited States. Postmaster General. Cost Ascertainment: Instruction Letter U; Record of Revenues by Classes on Drop Mails and Station Letter-box Collections by Railway Mail Service. U.S. GPO, 1932.
Warning: These citations may not always be 100% accurate.