Easton, Susan M., author
Routledge, [date of publication not identified]
Buku Teks
Russel, Bertrand, author
George Allen and Unwin, 1922
Buku Teks
Reckless, Walter
Buku Teks
Reckless, Walter C., author
Appleton-Century-Crofts, 1961.
Buku Teks
Andrews, Richard, author
Open University Press, 1991
Buku Teks