Bogdanskii, Y. V., and Y. Y. Sanzharevskii. “The Dirichlet Problem With Laplacian With Respect to a Measure in the Hilbert Space”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 6, June 2014, pp. 733–739, https://umj.imath.kiev.ua/index.php/umj/article/view/2174.