Robinson, James A
The Bobbs-Merrill Company,Inc., 1963
Buku Teks
Burdette, Franklin L.
Princeton, Princeton University Press
Buku Teks
Findlay, Bruce Allyn
Stanford University Press, 1952
Buku Teks
Findlay, Bruce Allyn
Stanford University Press, 1959
Buku Teks
Solomon, Lewis D.
West Publishing Co, 1993
Buku Referensi