Lewis, William Arthur, author
University of Ghana by the Ghana Pub, 1971
Buku Teks
McNamara, John E.
Digital Press, 1982
Buku Teks
Streffer, Christian, author
Springer-Verlag, 2011
eBooks
edited by Fatimah Kari ...[and others]
University of Malaya , 2006
Buku Teks
Meier, Gerald M., author
Oxford University Press, 1984
Buku Teks