Krutitskii, P. A., and N. Ch. Krutitskaya. 2008. “The Harmonic Dirichlet Problem in a Planar Domain With Cracks”. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica 7 (November):113-23. https://studmath.uken.krakow.pl/article/view/13273.