John Wiley & Sons, 1970
Buku Teks
Oxford University Press, 1995
Buku Teks
Head, Sydney W.
Houghton Miffiln, 1987
Buku Teks
Makin, John H.
American Entreprise Institute, 1991
Buku Teks
Bernardo, C. Joseph
Military Service Division, Stackpole Co., 1961
Buku Teks