Hill, L.A.
Oxford University Press, 1977
Buku Teks SO
Foers, E.
Oxford University Press, 1957
Buku Teks SO
edited by Gareth Williams, Martin Kenyon and Lynn Williams
Overseas Student Trust, 1987
Buku Referensi
British Council, 1980
Buku Teks
by British Council
British Council, 1959
Buku Teks SO