Title: Generalized Hölder's inequality on Morrey spaces,
Abstract: The aim of this paper is to present necessary and sufficient conditions for
generalized Hölder's inequality on generalized Morrey spaces. We also
obtain similar results on weak Morrey spaces and on generalized weak Morrey
spaces. The necessary and sufficient conditions for the generalized
Hölder's inequality on these spaces are obtained through estimates for
characteristic functions of balls in $\mathbb{R}^d$.