Axelbank, Albert
Hill and Wang, 1972
Buku Teks
O`Dell, Scott
Houghton Miffiln, 1988
Buku Teks
Vagts, Alfred, author
Greenwood Press, 1959
Buku Teks
edited by Kenneth Fidel
Transaction Books, 1975
Buku Teks
Potgieter E. J.
W.E.J Tjeenk Willink, 1914
Buku Teks