Member of the Scientific Council of the Stefan Banach International Mathematical Center, Warszawa, Poland
Director of the Teylers Foundation
Chair of the Scientific Advisory Board of the Leiden Observatory
Member of the board of Computer Algebra Nederland
Member of the board of Econophysics
Associate editor SIAM Journal on Mathematical Analysis
Member editorial board Integral Equations and Operator Theory
Member editorial board Functional Differential Equations
Member editorial board Concrete Operators