A., M. R., M. F. A, C. Yong, M. Khalis, M. S. S., and S. A. “Soil Enhancement Material Using Palm Oil Ashes (POA) for Grounding Purposes”. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), vol. 8, no. 7, Oct. 2016, pp. 47-50, https://jtec.utem.edu.my/jtec/article/view/1277.