“…In [21], a direct method of moving planes on fractional equations was introduced to obtain symmetry and nonexistence of solutions for nonlinear equations involving the fractional Laplacian on various domains. This method has become a powerful tool in investigating qualitative properties of fractional equations and has been applied by numerous researchers to solve a wide variety of problems (see [9,11,17,18,19,20,21,27,28,12,29,35,36,42,43,56,68,69,73,71,75,76,80,79,91,94,96,102,103,101] and the references therein). This idea was then modified in [19] [20] to study equations involving fully nonlinear nonlocal operators and degenerate nonlinear nonlocal operators such as fractional p-Laplacians, and obtained symmetry, monotonicity, and nonexistence of solutions.…”