PREFACE Vil 
feedback control, and the Laplace transformation, it is possible to use 
this book in a senior course. The material has also been used as the 
basis of a seminar in which literature study was the main element of the 
course. 
The authors have been engaged in the study of sampled-data systems 
for a number of years and have supervised doctoral research in this 
field at Columbia University and presently at Stanford University as 
well. A strong impetus to the advancement of this activity was and is 
now provided by the United States Air Force Office of Scientific Research, 
under whose auspices much of the research in sampled-data systems 
was done at Columbia University. This support is gratefully acknowl- 
edged by us, our colleagues, and graduate students. 
An attempt to list all those individuals who have been of assistance to 
us in one way or another would surely lead to the embarrassment of 
having omitted some. Risking this, however, we shall mention a few 
and recognize their many suggestions with thanks. Included are 
Professors Lotfi A. Zadeh, John E. Bertram, George M. Kranec, and 
Bernard Friedland, Dr. Rudolph E. Kalman, and the many graduate 
students and research assistants with whom we have been associated. 
JoHN R. RAGAZZINI 
GENE F, FRANKLIN 
