Wormald, Avison
Pan Books, 1973
Buku Teks
Michael R. Czinkota, Ronkainen Ilkka A., Michael H.Moffett, Eugene O. Moynihan, ... [et al.].
Harcourt College publishers, 2001
Buku Teks
Dymsza, William A.
McGraw-Hill, 1972
Buku Teks
Martyn, Howe
Lexington Books, 1972
Buku Teks
Globerman, Steven
Prentice-Hall, 1986
Buku Teks