Elliott, Philip, author
Herder and Herder, 1972
Buku Teks
Carr-Saunders, A. M., author
Clarendon Press, 1933
Buku Teks
Schrag, Clarence C., author
Harper & Row, 1963
Buku Teks
Ginsberg, Morris
Buku Teks
Zanden, James W. Vander, author
John Wiley & Sons, 1979
Buku Teks