Lang, N. D., T. G. Lich, and L. Duc. “Two Approximation Methods of Spatial Derivatives on Unstructured Triangular Meshes and Their Application in Computing Two Dimensional Flows”. Vietnam Journal of Mechanics, vol. 28, no. 4, Dec. 2006, pp. 230-4, doi:10.15625/0866-7136/28/4/5584.