Holmes, Parker M.
South-Western Publishing Co., 1960
Buku Teks
edited by Joseph Seibert & Gorden [i.e. Gordon] Wills
Penguin Books, 1970
Buku Referensi
Aaker, David A., author
John Wiley & Sons, 1995
Buku Teks
Churchill, Gilbert A., author
Thomson, 2005
Buku Teks
Cooper, Donald R., author
McGraw-Hill/Irwin, 2006
Buku Teks