“…The proofs of the two latter results fall under the well-known scope of the general (vector-valued) Calderón-Zygmund theory for spaces of homogeneous type. Analogous approach based on the Calderón-Zygmund theory in similar situations can be found in [8,14,22,25,26,28,29,30,34,40,41,42,43,44], among many others. For the reader's convenience we recall the main ingredients of this theory in what follows.…”