DovgosheiA. A. “Some Properties of Polynomials Orthogonal in a Space With ‘intermediate’ Topology. Kernel Function and Extremal Properties”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 45, no. 7, July 1993, pp. 915–923, https://umj.imath.kiev.ua/index.php/umj/article/view/5884.