Fox, Roy
McGraw-Hill, 1991
Buku Teks
Robertson, A.G.
Thomas Nelson & Sons , 1971
Buku Teks
Fandy Tjiptono, author
Andi Offset, 2003
Buku Teks
Strategic Direction Publishers, [date of publication not identified]
Buku Referensi
Strategic Direction Publishers, [date of publication not identified]
Buku Referensi