Maugesten, Paul Aleksander, and Torgunn Karoline Moe. “The $2$-Hessian and Sextactic Points on Plane Algebraic Curves”. MATHEMATICA SCANDINAVICA 125, no. 1 (August 29, 2019): 13–38. Accessed April 25, 2024. https://www.mscand.dk/article/view/114715.