Humphreys, Christmas, author
Penguin Books, 1985
Buku Referensi
Mumford, Lewis, author
Harcourt , 1961
Buku Teks
McDonald, Lee Cameron, author
Harcourt, Brace & World, 1968
Buku Teks
Pak, Pyong-son, author
Jimoondang, 2003
Buku Teks
Milner, Richard
Facts On File, 1990
Buku Referensi