Rungrodnimitchai, Supitcha, Wachira Phokhanusai, and Natthapong Sungkhaho. 2017. “Preparation of Silica Gel from Rice Husk Ash Using Microwave Heating”. Journal of Metals, Materials and Minerals 19 (2). Bangkok, Thailand. https://jmmm.material.chula.ac.th/index.php/jmmm/article/view/235.