Potapov, M. (2007) “A more accurate threshold in bilateral control and observation problems for the wave equation”, Numerical Methods and Programming (Vychislitel’nye Metody i Programmirovanie), 8(12), pp. 147–153. Available at: https://en.num-meth.ru/index.php/journal/article/view/256 (Accessed: 29 April 2024).