“…On the other hand, in the last two decades, many classical results concerning the Calderón-Zygmund operators and function spaces have been proved still valid for metric spaces equipped with non-doubling measures; see, for example, [5,6,15,18,29,30,[38][39][40][41][42]. In particular, let μ be a non-negative Radon measure on R d which only satisfies the polynomial growth condition that there exist some positive constant C 0 and n ∈ (0, d ] such that, for all x ∈ R d and r ∈ (0, ∞), μ(B(x, r )) ≤ C 0 r n , (1.2) where B(x, r ) := {y ∈ R d : |x − y| < r }.…”