edited by John C. Caldwell and Chukuka Okonjo
Longmans, Green, 1968
Buku Teks
Coughlan, Robert, author
Time Incorporated, 1962
Buku Teks
by William Brass ... [et al.]
Princenton University Press, 1968
Buku Teks
Marcus, Edward, author
Bookman Associates, 1960
Buku Teks
Due, John F., author
MIT Press, 1963
Buku Teks