A retrospective on input-output stability theory

This short paper is a written version of one part of the plenary address gi ven at the November 1999 NOLTA symposium held at the Hilton Waikoloa Villag e in Hawaii. I was invited by Professor Shin'ichi Oishi, a general vice-cha irman of the symposium, to give a survey of some of my own research. I was happy to do that-in the context of a description of what Bell Labs.' resear ch environment was like in its math center in the 1960's, and why I feel th at today's young researchers are often too constrained in that they are typ ically not encouraged to try to do really interesting work. Here the emphas is is on only the origins of input-output stability theory.