%0 Journal Article
%A Tadeusz Kulczycki
%T On concavity of solutions of the Dirichlet problem for the equation $(-\Delta)^{1/2} \varphi = 1$ in convex planar regions
%J Journal of the European Mathematical Society
%D 2017
%P 1361-1420
%V 19
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/articles/10.4171/jems/695/
%R 10.4171/jems/695
%F JEMS_2017_19_5_a2