Dung, H. Đình, and T. X. Bộ. “Defference Schemes for Weak Solutions of Mixed Problem for a Class of Hyperbolic Differential Equations I”. Journal of Computer Science and Cybernetics, vol. 19, no. 3, July 2012, pp. 217-26, doi:10.15625/1813-9663/19/3/1528.