edited by R.P. van de Riet and W. Litwin. edited by K. A. van der Hucht, and G. Vaiana. edited by J.K. van der Korst. edited by W. L. Van der Poel and L. A. Maarssen. edited by A. van der Laan and A.A. Winters. edited by A.F. Clark and R.P. Reed and G. Hartwig. edited by C.J. van Rijsbergen. edited by J.D. Collinson and J. Lewin. edited by G.M.A. van Beynum, J.A. Roels. edited by Fred Erisman and Richard W. Etulain.