Lever-Tracy, Constance
Routledge & Kegan Paul, 1988
Buku Teks
Pike, Douglas, 1908-1974, author
Cambridge University Press, 1970
Buku Teks
edited by Gordon Greenwood
Angus and Robertson, 1969
Buku Teks
Younger, R. M.
Victoria Hutchinson Group 1982
Buku Teks
Ward, Russel, author
Prentice-Hall, 1965
Buku Teks