Evi Triwulandari, et al. “EFFECT OF NCO OH RATIO AND MOLD SYSTEM ON PHYSICAL AND MECHANICAL PROPERTIES OF RIGID POLYURETHANE FOAM BASED ON PALM OIL”. Jurnal Sains Materi Indonesia, vol. 12, no. 2, Feb. 2011, pp. 96-100, doi:10.17146/jsmi.2011.12.2.4593.