Schiffman, Leon G., author
Pearson, 2015
Buku Teks
Ferber, Robert
McGraw-Hill Book Co., Inc. , 1949
Buku Teks
Hoyer, Wayne D., author
South Western Cengage Learning, 2012
Buku Teks
The University of North Carolina Press, 1974
Buku Teks
Schiffman, Leon G., author
Pearson Education, Inc., 2007
Buku Teks