“…Moreover, there exists a positive constant C such that |B((x, t), r)| = Cr Q , where Q = 2d + 2 is the homogeneous dimension of H n and |B((x, t), r)| is the Lebesgue measure of the ball B((x, t), r). Obviously, the triplet (H n , d, dx) satisfies the doubling condition (8).…”