Davis, Con, author
Longman, 1991
Buku Teks
editor, Josephine Donovan
University Press of Kentucky, 1975
Buku Teks
Walker, William, author
Cambridge University Press, 2009
eBooks
Longman , 1988
Buku Teks
Compiled and edited by Dorothy Nyren Curley, Maurice Kramer, Elaine Fialka Kramer
Continuum, 1989
Buku Referensi