Jiggins, Chris D., author
Oxford University Press, 2017
eBooks
Mufwene, Salikoko S, author
Cambridge University Press , 2001
Buku Teks
edited by John L. Gittleman
Comstock , 1989
Buku Teks
Richardson, W. Norman, author
Macmillan, 1976
Buku Teks
edited by Peter Moore, R.J. Berry and A. Hallam
Grolier International, 1993
Buku Referensi