Plum, Werner
Hildesheimer Druck-und Verlags-GmbH, 1974
Buku Teks
Lydall, Harold
Oxford University Press, 1984.
Buku Teks
Russell, Bertrand, 1872-1970, author
George Allen & Unwin Ltd, 1949
Buku Teks
Longman Cheshire, 1991
Buku Teks
Ebenstein, William, author
Prentice-Hall, 1967
Buku Teks