The present monograph is the second volume in the natural extension of the prior 2-volume work with the same title and by the same authors, which encompassed findings up until 2014. This four-volume project encapsulates the authors’ decade-long research in the trending topic of nonstandard function spaces and operator theory.

Among other things, this volume treats interpolation and extrapolation problems, boundedness criteria for multilinear fractional integrals in classical and grand Lebesgue spaces, and focusses on Morrey-type and Herz spaces.

The book is aimed at an audience ranging from researchers in operator theory and harmonic analysis to experts in applied mathematics and post graduate students. In particular, it is hoped that this book will serve as a source of inspiration for researchers in abstract harmonic analysis, function spaces, PDEs and boundary value problems.