MotornayaO. V., MotornyiV. P., and NitiemaP. K. “One-Sided Approximation of a Step by Algebraic Polynomials in the Mean”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 62, no. 3, Mar. 2010, pp. 409–422, https://umj.imath.kiev.ua/index.php/umj/article/view/2876.