Ellis, Sue, editor
Cambridge University Press, 2011
eBooks
Lado, Robert, author
University of Michigan, 1957
Buku Teks
Centre for language in primary education, 1990
Buku Teks
Dougill, Peter
Open University Press, 1993
Buku Teks
Wray, David
Routledge, 1991
Buku Teks