Walker, William, author
Cambridge University Press, 2009
eBooks
Runge, Laura L., author
Cambridge University Press, 1997
eBooks
Lecercle, Jean-Jacques, author
Routledge, 1994
Buku Teks
Juhl, P.D.
Princeton University Press, 1980
Buku Teks
Ward, A.C., author
Longman, 1955
Buku Teks