C.S, L., O. T.L, C. C.H, and A. S. “Effect of Isocyanate Index on Physical Properties of Flexible Polyurethane Foams”. Malaysian Journal of Science, vol. 26, no. 2, Aug. 2007, pp. 91-98, https://juku.um.edu.my/index.php/MJS/article/view/8069.