Nairobi, Nairobi, et al. “Dynamic Modeling Data Export Oil and Gas and Non-Oil and Gas by ARMA(2,1)-GARCH(1,1) Model: Study of Indonesian’s Export over the Years 2008-2019”. International Journal of Energy Economics and Policy, vol. 10, no. 6, Oct. 2020, pp. 175-84, https://econjournals.com./index.php/ijeep/article/view/9892.