Bussaya Rattanasupa and Wirunya Keawwattana, “The Development of Rubber Compound based on Natural Rubber (NR) and Ethylene-Propylene-Diene-Monomer (EPDM) Rubber for Playground Rubber Mat”, Agr. Nat. Resour., vol. 41, no. 5, pp. 239–247, Dec. 2007.