Williams, David, author
Sweet & Makwell, 2000
Buku Teks
Leslie, Douglas L., author
West Publishing, 1992
Buku Teks
Champion, Walter T, author
WEST , 2009
Buku Teks
Smucker, Bob
Jossey - Bass Publishers, 1991
Buku Teks
Pearson, Michael W., author
Pearson education, 2015
Buku Teks