Haryono, Agus, et al. “Control of Biodegradability of Polyurethane Foam Based on Palm Oil by Ratio of Soft Segment on the Polymer Backbone”. Annales Bogorienses, vol. 14, no. 1, June 2010, pp. 11-17, doi:10.14203/ann.bogor.2010.v14.n1.11-17.