O. A.  Awoyinka, Oyewole, I. O., Amos, B. M. W., and Onasoga, O. F., ?Comparative pesticidal activity of dichloromethane extracts of Piper nigrum against Sitophilus zeamais and Callosobruchus maculatus?, African Journal of Biotechnology, vol. 5, pp. 2446 - 2449, 2006.