Adams, Walter, 1922-1998
Macmillan, 1957
Buku Teks
edited by Theodore L. Becker and Vernon G. Murray
Oxford University Press, 1971
Buku Teks
Seckler-Hudson, Catheryn
United State Information Service, 1959
Buku Teks
The America University, [date of publication not identified]
Buku Teks
Palumbo, Dennis J.
Harcourt Brace College, 1994
Buku Teks SO