In J. Class. Anal. 26 (2025), 63–76, we proved that the discrete Riesz potential Iα is a bounded operator Hp(Zn)→Hq(Zn) for n−1n<p≤1, 1q=1p−αn and 0<α<n. In this note, we extend this result to the full range 0<p≤1.
Pablo Rocha (Fri,) studied this question.