edited by J.W. de Bakker and J.C. van Vliet. edited by J.J. Becker and J.C. Bonner. edited by J. T. Devreese and V. E. van Doren. edited by J.W. Stucki and W.L. Banwart. edited by B. Bernier and C. H. Winget. edited by J.Boogaard and G.M.van Dijk. edited by J.C. Allen and R.J. Hamilton. edited by N.J.W. Kreger-van Rij.