Coleman, Frank M
University Toronto Press, 1977
Buku Teks
Osborn, Annie Marion
Oxford University Press, 1940
Buku Teks
Allen, J. W., author
Methuen, 1951
Buku Teks
McClelland, J.S.
Routledge , 1998
Buku Teks
Mason, Alpheus Thomas,1899-1989, author
Prentice-Hall, 1959
Buku Teks