Mufwene, Salikoko S
Cambridge University Press , 2001
Buku Teks
edited by John L. Gittleman
Comstock , 1989
Buku Teks
Richardson, W. Norman
Macmillan, 1976
Buku Teks
edited by Peter Moore, R.J. Berry and A. Hallam
Grolier International, 1993
Buku Referensi
Boughey, Arthur S.
McMillan Publisher, 1975
Buku Teks