Munawaroh, M., I. Ghozali, F. Fuad, and F. Faisal. “The Trade-off Strategy Between Financial and Environmental Performance: Assessment of Sustainable Value Added”. International Journal of Energy Economics and Policy, vol. 8, no. 1, Jan. 2018, pp. 5-11, https://www.econjournals.com/index.php/ijeep/article/view/5913.