Davidson, Paul, author
Edward Elgar, 2011
Buku Teks
Young, Warren C., author
Westview, 1987
Buku Teks
Dillard, Dudley D., author
Prentice-Hall, 1949
Buku Teks
Torr, Christopher, author
Westview Press, 1988
Buku Teks
Nentjes, A.
Samson, 1988
Buku Teks