USDHEW, 1970
Buku Teks
Carroll, Stephen J.
Dorling Kindersley , 1992
Buku Referensi
edited by Clyde V. Kiser
Princeton University Press, 1964
Buku Teks
Princenton University Press, 1970
Buku Teks
edited by Clyde V. Kiser
Princeton University Press, 1962
Buku Teks