Vaillant, George C.
Penguin Books, 1950
Buku Teks
Donnelly, Thomas C.
The University of New mexico Press, 1953
Buku Teks
Pick, James B.
Westview , 1989
Buku Referensi
Dullemen, Inez van
Querido, 1988
Buku Teks
Myers, Charles Nash
Princeton University , 1965
Buku Teks