Frederic Grare, Amitabh Mattoo, editor
Manohar, 2001
Buku Teks
Parkin, Raleigh
Green & Company, Canada, 1945
Buku Teks
Hardgrave, Robert L., author
Harcourt, Brace, 1970
Buku Teks
Brecher, Michael
Frederick A. Praeger, 1966
Buku Teks
Sharan, P.
Metropolitan, 1984
Buku Teks