Milton-Edwards, Beverly
Routledge, 2003
Buku Teks
Cook, Chris
Longman, 1991
Buku Referensi
Walz, Jay
Atheneum, 1966
Buku Teks
Goldschmidt, Arthur
Westview Press, 1983
Buku Teks
edited by Sydney Nettleton Fisher
Cornell University Press , 1955
Buku Teks