Schultz, Heidi, author
McGraw-Hill, 2006
Buku Teks
Bovee, Courtland L., author
Prentice-Hall, 2005
Buku Teks
Holt, Rinehart and Winston of Canada, Limited, 1988
Buku Teks
Young, Dona J., author
McGraw-Hill, 2006
Buku Teks
Quible, Zane K., author
Prentice-Hall, 1996
Buku Teks