communications of the "van der waals-fund" Isotherms of CO2 between 0ÿê and 100ÿê C / G.P. Nijhoff, A.J.J. Gerver S.J. and A. Michels communications of the "van der waals-fund" measurement of the viscosity of gases at high pressures; The viscosity of nitrogen to 1000 atms / A. Michels and R.O. Gibson mitteilungen des "van der waals-fonds" Zur Dispersionstheorie des Schalles / A.J. Rutgers communications of the "van der waals-fund" Isotherms of nitrogen between 0ÿê and 150ÿê and at pressures from 20 to 80 atm / A. Michels, H. Wouters and J. de Boer