Donal O’Regan is a Professor at the National University of Ireland. His research interests are in nonlinear functional analysis. His previous publications with Springer include “Constant-Sign Solutions of Systems of Integral Equations” (978-3-319-01254-4) and “Fixed Point Theory for Lipschitzian-type Mappings with Applications” (978-0-387-75817-6), both as a co-author.
