Tousley, Rayburn D.
Macmillan , 1962
Buku Teks
Czinkota, Michael R., author
South Western Cengage Learning, 2010
Buku Teks
Alserhan, Baker Ahmad, author
Gower, 2016
Buku Teks
Keegan, Warren J., author
Prentice-Hall, 1997
Buku Teks
Bearden, William O., author
McGraw-Hill/Irwin, 2004
Buku Teks