Hardgrave, Robert L., author
Harcourt, Brace, 1970
Buku Teks
Brecher, Michael
Frederick A. Praeger, 1966
Buku Teks
Cambridge University Press, 2009
eBooks
Baxi, Smita J., author
Abhinav Publications, 1973
Buku Teks
Cambridge University Press, 2004
Buku Teks