Winham, Gilbert R.
University of Toronto Press, 1992
Buku Teks
Cambridge University Press, 2009
eBooks
Ahghari, Zohreh
Florida state university, 1991
Buku Teks
Hylton, Keith N, Author
Cambridge University Press, 2003
eBooks
Ranney, Austin, author
American Enterprise Institute, 1985
Buku Teks