Warsono, Warsono, et al. “Vector Autoregressive With Exogenous Variable Model and Its Application in Modeling and Forecasting Energy Data: Case Study of PTBA and HRUM Energy”. International Journal of Energy Economics and Policy, vol. 9, no. 2, Feb. 2019, pp. 390-8, https://www.econjournals.com/index.php/ijeep/article/view/7223.