Furnivall, JS
Solidaridad publishing house, 1974
Buku Teks
Wilding, Michael, author
Penguin Books , 1984.
Buku Teks
edited Joseph Friedman and Daniel H. Weinberg
Sage, 1983
Buku Teks
Keegan, William, author
Allen Lane, 1984
Buku Teks
Kohn, Hans, author
D. Van Nostrand, 1965
Buku Teks