Cita APA (7th ed.)
Nyrop, R. F. (1969). . U.S government printing office.
Cita Chicago (17th ed.)
Nyrop, Richard F. . Washington D.C: U.S government printing office, 1969.
Cita MLA (9th ed.)
Nyrop, Richard F. . U.S government printing office, 1969.
Atenció: Aquestes cites poden no estar 100% correctes.