Reference Request – Fractional Laplacian Border Regularity Type Results

Let $ u $ to be a solution of $ – Delta u = f text {in} Omega $ with $ u = 0 text {on} partial Omega. $ Yes $ f in L ^ 2 ( Omega) $then $ u in H ^ 2 ( Omega) cap H ^ {1} _ {0} ( Omega) $provided $ Omega $ is a smooth bounded domain.

Is this type of theorem true for the equation $ (- Delta) ^ u = f text {in} Omega $ with $ u = 0 text {in} mathbb R ^ N – Omega $ with $ 0 <s <1. $