Ferreya, E., T. Godoy, and M. Urciuolo. “$L^p-L^q$ Estimates for Singular Fractional Integral Operators”. MATHEMATICA SCANDINAVICA 84, no. 2 (June 1, 1999): 213–230. Accessed April 28, 2024. https://www.mscand.dk/article/view/13876.