Yoo, Yeol-su
Yekyong Publishing Co., 2002
Buku Referensi
Gwon, Sung-ung
Naramal, 2007
Buku Teks
Methopld, Ken
Compass Publishing, 2007
Buku Teks
Methopld, Ken
Compass Publishing, [Date of publication not identified]
Buku Teks
Seoul-Somerset Jimoondang Publishing 2000
Buku Teks