edited by Peter Moore, R.J. Berry and A. Hallam
Grolier International, 1993
Buku Referensi
edited by Ian R. Swingland and Paul J. Greenwood
Clarendon Press, 1983
Buku Teks
Louw, Gideon N., author
Longman Scientific and Technical, 1993
Buku Teks
edited by Peter Slater and R. McNeill Alexander
Grolier International, 1986
Buku Referensi
Mufwene, Salikoko S, author
Cambridge University Press , 2001
Buku Teks