M. Y. . Petunina, “Average quadratic error of the estimate of the first order splines in the model of linear regression”, Ukr. Mat. Zhurn., vol. 43, no. 3, pp. 429–432, Feb. 1991, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/9628