Proof of Theorem 1 Without loss of generality, we may assume that and . Pick any ball , and write
where . Hence, we have
(6)
By the boundedness of (see Theorem 3 in [5]), we obtain
(7)
Now, for and using Lemma 3, we have
(8)
where
and
Then
(9)
By the proof of Theorem 1.1 in [3], we have
Next we deal with . For , . We get
Let . By simple computation, . By the definition of ,
(10)
where and .
Using Hölder’s inequality, (10), and the boundedness of the fractional integral with , for , we have
(11)
For , using Lemma 2, we get
(12)
It is easy to check that . Furthermore, using Corollary 1, we have
(13)
Therefore, by (13),
(14)
where we choose N large enough so that the above series converges.
From (6)-(14), we obtain
Thus, Theorem 1 is proved. □
Proof of Theorem 2 During the proof of Theorem 2, we always denote . Without loss of generality, we may assume that , , and . Pick any ball , and write
where . Hence, we have
(15)
By the boundedness of (see Theorem 2 in [8]), we obtain
(16)
Set . Write . Then
(17)
By (8) in the proof of Theorem 1, we obtain
Let . By simple computation, . By Lemma 4, . Then
(18)
By Lemma 1 and Corollary 2, as well as Lemma 3, we have
(19)
where we choose N large enough so that the above series converges.
For , we assume due to Lemma 3. Then, since , we also have . Then
By (11) and (12) in the proof of Theorem 1, we obtain
(20)
if we choose N large enough.
Now, for and using Lemma 3, we have
(21)
where
and
Then,
(22)
Firstly, we consider . By Proposition 2 and (10), for , we have
(23)
Then we get
(24)
where we choose N large enough so that the above series converges.
For , then for . Using Lemma 2, we get
(25)
Let . We choose u such that and .
Let . By simple computation,
Finally, we deal with . Using Hölder’s inequality, (10), and the boundedness of the fractional integral , for , we have
(26)
Then
(27)
where we choose N large enough so that the above series converges.
From (15)-(27), we obtain
Thus, we complete the proof of Theorem 2. □