“…Since then the research on equations of the form (1.2) has flourished once more, mostly with A being the Dirichlet Laplacian or Dirichlet (rarely regional) fractional Laplacian. We limit ourselves to mentioning [3,15,22,38,43,45] in case of Dirichlet Laplacian or divergence form diffusion operators and [16,17,18,35,37] in case of the fractional Laplacian.…”