Some regularity results in small Lebesgue spaces for the weak or the very weak solution of the linear equation $-\Delta u = f$ are given, improving all the previous results obtained in the usual Lebesgue spaces. Some of our results have been derived using borderline Sobolev embeddings related to the Grand Lebesgue spaces. So, we provide new Sobolev inclusions using the Generalized Gamma spaces and generalizing the Fusco-Lions-Sbordone results.
"Pointwise estimates for $G\Gamma$-functions and applications." Differential Integral Equations 30 (11/12) 809 - 824, November/December 2017.