LasuriyaR. A. “Summation of Fourier-Laplace Series in the Space $L(S^m)$”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 57, no. 4, Apr. 2005, pp. 496–504, http://umj.imath.kiev.ua/index.php/umj/article/view/3616.