Strearn, William T.
David & Charles, 1983
Buku Referensi
Bauer, Lauria
London : Routledge, 1998
Buku Teks
Morgan, John, 1944-2004
Oxford University Press, 1990
Buku Teks SO
Sass, John E.
Iowa State University Press, 1994
Buku Teks
Cook, Peter, 1936
Academy Editions, 1996
Buku Teks