Bureau of International Information Programs United States Department of State, 2004
Buku Teks
Epps, Garrett, author
Oxford Univesity Press, 2013
Buku Teks
edited by Alexander T.J. Lennon
MIT Press, 2002
Buku Teks
Goodyear Publishing Company, Inc., 1973
Buku Teks
Schikele, Rainer, author
McGraw-Hill, 1954
Buku Teks