“…The tool used in this paper is the parametrix method, proposed by E. Levi [58] to solve elliptic Cauchy problems. It was successfully applied in the theory of partial differential equations [27], [62], [19], [24], with an overview in the monograph [25], as well as in the theory of pseudo-differential operators [22], [44], [48], [54], [68]. In particular, operators comparable in a sense with the fractional Laplacian were intensively studied [20], [21], [51], [53], [22], also very recently [16], [40], [15], [55].…”