ABSTRACT
AND now this great master has left us. No one who has been close to him both personally and scientifically would be able to describe the feeling that lies heavy on all of us. No words can express what he has been to us, and few of us if any will have yet resigned ourselves to the realization that from now on there is to be an impenetrable wall separating us from him, from his advice, his encouragement, his critical guidance-and that the road ahead will have to be traversed without him.
