“…Within the control systems area, there was for example work on linear-quadratic optimization problems, Lyapunov stability, circle and Popov criteria and positive real transfer functions; see for example [8], [24], [25], [10], [38], [6], [15], [7], [16], [11], [27]. In the area of signal processing, there was work on Kalman filtering and its derivatives, detection of frequency modulated (FM) signals, spectral factorization, and pulse frequency modulation; see for example [42], [45], [46], [54], [57], [64], [66], [67], [69]. [71], [72], [76].…”