Hassan, C. R. C., M. J. Pitt, and A. J. Wilday. “Integrating Performance Indicator Into the Audit Process Safety Management System”. ASEAN Journal of Chemical Engineering, Vol. 5, no. 2, Dec. 2005, pp. 161-8, https://dev.journal.ugm.ac.id/v3/AJChE/article/view/7646.