Johns Hopkins University Press , 1974
Buku Teks
Lewis, William Arthur, 1915-, author
Development, 1966
Buku Teks
Stolper, Wolfgang F., author
Harvard University Press, 1966
Buku Teks
Bower, P. A.
Faber and Faber Limited , 1948
Buku Teks
Aboyade, Ojetunji, author
Praeger, 1966
Buku Teks