Vaughan, Emmett J.
John Wiley & Sons, 1996
Buku Teks
Willett, Allan H.
University of Pennsylvania Press, 1951
Buku Teks
Vaughan, Emmett J.
John Wiley & Sons, 2001
Buku Teks
Hammond, J.D.
Foresman and Company, 1968
Buku Teks
Chin, Yee Wah
Pearson Prentice Hall, 2004
Buku Teks