C. Constanda, ON THE SOLUTION OF THE DIRICHLET PROBLEM FOR THE 2-DIMENSIONAL LAPLACE EQUATION, Proceedings of the American Mathematical Society, 119(3), 1993, pp. 877-884
The solution of the Dirichlet problem for the two-dimensional Laplace
equation is obtained as a modified single layer potential by a method
applicable even when the logarithmic capacity of the boundary curve is
equal to 1.