Simbolon, F., R. Dewanti, and I. Melati. “FORMULASI KOMPETENSI INTI GREEN NITROGEN DALAM LAYANAN NITROGEN DI SPBU PERTAMINA”. Journal of Business Strategy and Execution, vol. 5, no. 2, June 2013, pp. 201 -6, https://journal.binus.ac.id/index.php/JBSE/article/view/775.