Kelly, Curtis, author
Cambridge university press, 2010
Buku Teks
Messenger, William E., author
Prentice-Hall, 1989
Buku Teks
Spaventa, Lou J., author
McGraw-Hill, 2001
Buku Teks
Presley, John W., author
Holt, Rinehart and Winston, 1980
Buku Teks
Goldman, Stephen H., author
Houghton Miffiln, 1986
Buku Teks