by Colin Legu ... [et al.]
McGraw-Hill, 1980
Buku Teks
edited by John C. Caldwell and Chukuka Okonjo
Longmans, Green, 1968
Buku Teks
Hance, William A., author
Columbia University Press, 1970
Buku Teks
Williams, Robert, author
Gower, 1991
Buku Teks
by William Brass ... [et al.]
Princenton University Press, 1968
Buku Teks