Prawingwong, Piyawan, Chaiyan Chaiya, Prasert Reubroycharoen, and Chanatip Samart. 2017. “Utilization of Rice Husk Ash Silica in Controlled Releasing Application”. Journal of Metals, Materials and Minerals 19 (2). Bangkok, Thailand. https://jmmm.material.chula.ac.th/index.php/jmmm/article/view/237.