A.C. Kumoro, G.C. Ngoh, M. Hasan, C.H. Ong and E.C. Teoh
Asian Journal of Scientific Research 1 ( 4 ): 412 - 420 , 2008
Y.H. Ong, A.S.M. Chua and G.C. Ngoh
Journal of Applied Sciences 10 ( 21 ): 2643 - 2647 , 2010