Sotiris K. Ntouyas is a Professor Emeritus in the Department of Mathematics of the University of Ioannina, Greece. He received his Ph.D. from the University of Ioannina in 1980. His research interests include initial and boundary value problems for differential equations (ordinary, functional, with deviating arguments, neutral, partial, integro-differential, inclusions, impulsive, fuzzy, stochastic, fractional), inequalities, asymptotic behavior and controllability. More than 785 of his papers have appeared in print or have been accepted for publication in refereed journals. He is the co-author of five research monographs, a member of 21 international journals’ Editorial Boards, and a reviewer for many international journals. He appears in the 2018 list, published by Clarivate Analytics, of Highly Cited Researchers.