Routledge, 1997
Buku Teks
Kolodziej, Edward A, author
Cambridge University Press, 2005
Buku Teks
Nicholson, Michael, author
Cambridge University Press, 1989
Buku Teks
Douherty, James E., author
J.B. Lippincott, 1971
Buku Teks
Olson, William Clinton, author
Prentice Hall International, 1994
Buku Teks