Cambridge University Press, 1997
eBooks
Porter, Charles O. (Charles Orlando), 1919-2006, author
Macmillan, 1961
Buku Teks
Cheibub, Jose Antonio, author
Cambridge University Press, 2007
Buku Teks
edited by Eduardo P. Archetti
MacMillan Education, 1987
Buku Teks
Szulc, Tad, author
Atheneum, 1966
Buku Teks