Winpisinger, William W., author
Colorado Westview Press, 1989
Buku Teks
Gould, William B., IV, author
MIT Press, 1982
Buku Teks
Litwack, Leon, author
Prentice-Hall, 1962
Buku Teks
Rifkin, Bernard, author
McGraw-Hill, 1979
Buku Teks
Bok, Derek C., author
Simon and Schuster, 1969
Buku Teks