“…For the problems with a fractional Laplace operator, we refer to Liu and Tan [33], Liu et al [31], Migórski et al [35,38], Autuori and Pucci [1], Chen et al [9], Choi et al [12], Stinga and Torrea [44], Mosconi et al [39], Caffarelli et al [6], Chen et al [8]. On the other hand, for the problems dealing with multivalued terms modeled by Clarke's subdifferential we refer to the papers of Averna et al [2], Denkowski et al [13][14][15][16], Filippakis et al [18,19], Gasiński [20,21], Gasiński et al [22], Gasiński and Papageorgiou [24,25], Kalita and Kowalski [27], Papageorgiou et al [41,42], Zeng et al [48]. Finally, for the problems dealing with obstacle problems we refer to the papers of Caffarelli et al [4], Caffarelli et al [5], Choe [10], Choe and Lewis [11], Feehan and Pop [17], Oberman [40].…”