L.K, C., N. Mohd Tahir, and H. H.C.B. “Improved Method for the Determination of Cypermethrin in Sarawak Soils”. Malaysian Journal of Science, vol. 26, no. 1, Apr. 2007, pp. 109-17, http://mojes.um.edu.my/index.php/MJS/article/view/8047.