BurskiiV. P., and ShtepinaТ. V. “On the Spectrum of an Equivariant Extension of the Laplace Operator in a Ball”. Ukrains’kyi Matematychnyi Zhurnal 52, no. 11 (November 25, 2000): 1473-1483. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4554.