Bouquet, A.C.
Penguin Books, 1953
Buku Teks SO
Schroeder, Richard C.
International Communicational Agency, [date of publication not identified]
Buku Teks SO
edited by Nathan Glick
United Sates Information Agency, 1989
Buku Teks SO
United States Department of State, 1991
Buku Teks SO
Stokoe, William C.
University of Buffalo, 1960
Buku Teks SO