1. Kraner, H. W., Schroeder, G. L., Davidson, G., and Carpenter, J. W., Science, 152, 1235 (1966).
2. Adams, J. A. S., Barretto, P. M., Clark, R. B., and Duval, jun., J. S., Nature, 231, 174 (1971).
3. De Boer, The Dynamical Character of Adsorption (Clarendon Press, Oxford, 1953).
4. Ross, S., and Olivier, J. P., On Physical Adsorption (Interscience, New York, 1964).