Geoff Green, Ken Petford, Alan Short, David Walker
John Muray, 1975
Buku Referensi
The English Language , 1982
Buku Teks
American Association for the Advancement of Science, 2018
Majalah, Jurnal, Buletin
Ginn and Co., 1974
Buku Teks
Prentice-Hall, 1999
Buku Teks