edited by John L. Gittleman
Comstock , 1989
Buku Teks
Richardson, W. Norman
Macmillan, 1976
Buku Teks
Mufwene, Salikoko S
Cambridge University Press , 2001
Buku Teks
edited by Peter Moore, R.J. Berry and A. Hallam
Grolier International, 1993
Buku Referensi
Tullar, Richard M.
McGraw-Hill, 1977
Buku Teks