“…In fact, these two methods have been applied successfully to study equations involving nonlocal fractional operators (−∆) s (0 < s < 1), and a series of fruitful results have been achieved(see [4,16,20,21,26,27,28,37,43,45] and the references therein). There also got a series of fruitful results for fractional elliptic systems(see [11,39,41,42,46]) by moving planes. The disadvantage of the above mentioned approaches is that one need to impose some additional conditions on the solutions.…”