Gilbert, Martin
Avon books, 1997
Buku Teks
Stromberg, Roland N.
Prentice-Hall, 1997
Buku Teks
Thwaite, Anthony, author
Heineman, 1984
Buku Teks
edited by Clement Semmler
Oxford University Press, 1967
Buku Teks
Stoessinger, John G., author
Thomson Wadsworth, 2008
Buku Teks