S. G. Solodkii, “Optimization of projection schemes of digitization of ill-posed problems”, Ukr. Mat. Zhurn., vol. 51, no. 10, pp. 1398–1410, Oct. 1999, Accessed: Apr. 23, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4739