H. Barendregt , Nijmegen, The Netherlands.

H. Geuvers , Nijmegen, The Netherlands.

I. Moerdijk , Utrecht, The Netherlands.

J. van Oosten , Utrecht, The Netherlands.

B. Spitters , Nijmegen, The Netherlands.

W. Veldman, Nijmegen, The Netherlands.

S.A. Terwijn, Utrecht, The Netherlands.