Hasalli Hj Ibrahim, Nur, et al. “Study of Subsonic Airfoil Based on the Assessment of Lift- To-Drag (L D) Force Ratio”. International Journal of Engineering & Technology, vol. 8, no. 1.1, Jan. 2019, pp. 53-58, https://doi.org/10.14419/ijet.v8i1.1.24780.