The Unesco Press, 1974
Buku Teks
Clark, J. Desmond
Penguin Books Inc., 1959
Buku Teks
Routledge , 1996
Buku Teks SO
edited by Jacqueline A. Kalley, Elna Schoeman, Marlene Burger
University of South Africa, 2005
Buku Teks SO
Westview Press, 1980
Buku Teks SO