Kozlov, V., V. Maz’ya, and J. Rossmann. “Conic Singularities of Solutions to Problems in Hydrodynamics of a Viscous Fluid With a Free Surface”. MATHEMATICA SCANDINAVICA, vol. 83, no. 1, Sept. 1998, pp. 103-41, doi:10.7146/math.scand.a-13845.