edited by A. van Cauwenberghe. edited by A. van Itterbeek. edited by G. S. Landsberg. edited by C.J. van Rijsbergen. edited by G. van Oortmerssen. edited by Norman L. Weinberg. edited by Detlef Wildenberg. edited by E. van Oye. edited by Ivan Plander. edited by L. van der Hammen.