Schmidt, Steven
Prentice-Hall, 1983
Buku Teks SO
School Government Publishing Co., [date of publication not identified]
Buku Referensi
British Council, 1991
Buku Referensi
edited by Janet Moyles
McGraw-Hill, 2007
Buku Teks SO
edited by Japanese Government Team for Safeguarding Angkor (JSA)
Japan International Cooperation Center, 1995
Buku Referensi