Saad, S., M. Y. Abdullah, A. Salman, and N. Lyndon. “Ciri Dan Pengaruh Pemimpin Pendapat Dalam Kalangan Pekebun Kecil Kelapa Sawit: The Characteristics and Influence of Opinion Leaders on the Palm Oil Smallholders”. GEOGRAFI, vol. 6, no. 3, Nov. 2018, pp. 44-53, https://ojs.upsi.edu.my/index.php/GEOG/article/view/2100.