Zalizniak, V. “A Piecewise Exponential Method for the Numerical Simulation of Wave Propogation”. Numerical Methods and Programming (Vychislitel’nye Metody I Programmirovanie), vol. 7, no. 9, Oct. 2006, pp. 266-72, https://en.num-meth.ru/index.php/journal/article/view/218.