Korzyuk, V. I., and E.S. Cheb. “Cauchy Problem for a Linear Hyperbolic Equation of the Second Order”. Mathematical Modelling and Analysis 11, no. 3 (September 30, 2006): 275-294. Accessed December 22, 2024. https://journals.vilniustech.lt/index.php/MMA/article/view/9618.