Farrow, David
McGraw-Hill, 1994
Buku Teks
Harapan Bangsa Business School, 2012
Majalah, Jurnal, Buletin
edited by R. J. Chambers and G. W. Dean
Gerland Publishing, 1986
Buku Teks
Pizzey, Alan
Holt, Rinehart and Winston , 1980
Buku Teks
Warren, Carl S.
South-Western College, 1999
Buku Teks