Wriggins, W. Howard
Columbia University Press, 1969
Buku Teks
University of California Press, 1966
Buku Teks
Fitzgerald, Walter, author
Methuen, 1952
Buku Teks
Heard, Alexander
Anchor Books Doubleday and Company, 1962
Buku Teks
Routledge, 1997
Buku Teks