Howard, John A.
Richard D. Irwin, 1957
Buku Teks
Brown, F.E.
Addison Wesley c. , 1980
Buku Teks
Howard, John A.
Richard D. Irwin, 1962
Buku Teks
Kotler, Philip
Holt, Rinehart and Winston , 1971
Buku Teks
Kurtz, David L.
The Dryden Press , 1981
Buku Teks