Woytinsky, W.S., author
Twentieth Century Fund, 1953
Buku Teks
Bouvier, Leon F., author
Seven Lucks Press, 1999
Buku Teks
Thomlinson, Ralph
California State University, 1976
Buku Teks
Heer, David M., author
Prentice-Hall, 1975
Buku Teks
edited by Philip M. Hauser and Otis Dudley Duncan
The University of Chicago Press, 1959
Buku Teks