Saptono, A., S. Suparno, A. Wibowo, E. Ahman, I. Ismiyati, and D. Sukayugi. “An Analysis of Higher-Order Thinking Skills (HOTS) in the Learning of Economics”. International Journal of Learning, Teaching and Educational Research, vol. 19, no. 4, Apr. 2020, pp. 268-90, https://ijlter.myres.net/index.php/ijlter/article/view/397.