Spate, Oskar Hermann Kristian, author
Oxford University Press, 1965
Buku Teks
Holt, David H., author
Prentice-Hall, 1992
Buku Teks
Mulgan, Richard, author
Oxford University Press, 1989
Buku Teks
University of California Press, 1947
Buku Teks
Sinclair, Keith
Penguin Books, 1986
Buku Teks