Lougheed, Leslie Alan
Penguin Books, 1988
Buku Teks SO
by J. Swiericzuk ... [and others]
Pitman, 1980
Buku Teks
Williams, Morris
Longman, 1972
Buku Teks SO
edited by Greg Crouch, Ted Wheelwright, Ted Wilshire
Penguin Books, 1980
Buku Teks
Cheshire, 1974
Buku Teks