Ayu Esteka Sari, Pitriyani, I Gusti Ayu Purnamawati, Putri Mutira, Apri Wahyudi. “Subscription Economy Could Stimulate Gas Industry”. International Journal of Advanced Science and Technology, Vol. 29, no. 06, Apr. 2020, pp. 1799 -02, http://sersc.org/journals/index.php/IJAST/article/view/12874.