Shuker, Roy
Routledge , 1998
Buku Teks
Westrup, J. A., author
William Collins Sons, 1959
Buku Referensi
Dodd, Mead & Company, 1956
Buku Referensi
edited by Denis Arnold
Oxford University Press, 1992
Buku Referensi
Andy Bennett, Steve Waksman
SAGE, 2015
Buku Teks