Stewig, John Warren
Wadsworth, 1995
Buku Referensi
Centre for language in primary education, 1990
Buku Teks
Dougill, Peter
Open University Press, 1993
Buku Teks SO
Ellis, Sue, editor
Cambridge University Press, 2011
eBooks
Wray, David
Routledge, 1991
Buku Teks