“…Another main reason is that the fractional Laplacian (−∆) s (s ∈ (0, 1)) is a non-local operator comparing with the classical Laplacian −∆ which is a local one, the methods which were previously developed, maybe not be applied directly. We refer the interesting readers to see the recent progresses such as [9,13,15,17,20,19,32,33,34,41,39,42,44,45,46,48] and the references therein.…”