Eliahu I. Jury - IEEE Control Systems Society

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HISTORICAL PERSPECTIVES

Eliahu I. Jury KAMAL PREMARATNE

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o me, Eliahu I. Jury is more than an influential researcher who has made a long-lasting impact on the field of discrete-time systems and whose contributions appear in almost every text in control theory. For me, writing about Prof. Eliahu I. Jury takes a more personal tone. He has been my Ph.D. advisor, a coauthor, a colleague, a family friend, a trusted mentor to whom I constantly turn for valuable advice, and a person whom I hold in the highest regard and for whom I have great respect and admiration. After deliberating on how I should begin this tribute, I thought it apt to borrow the citation of the Egleston Medal, the highest award given by the Columbia University Engineering School Alumni Association, which was presented to Prof. Jury in 1999: “Academician who initiated the field of discrete-time systems, pioneered the z-transforms and created the ‘Jury stability test’.” With the burdens and pressures of professional and personal life, it is not often that we get an opportunity to stop and reflect on the pioneering researchers who have paved the way for us. The Egleston Medal citation is sufficient testimony to the long-lasting impact that Prof. Jury has had on discrete-time systems. I was fortunate to receive direction, guidance, and supervision from Prof. Jury while I was a graduate student at the University of Miami and to have him as a mentor and friend to this very day.

IN IRAQ AND ISRAEL 1923–1947 Eliahu (or Eli, as most of his colleagues call him) Ibrahim Jury was born on May 23, 1923, in Baghdad, Iraq, which was then home to a culturally and commercially vibrant Jewish community. He received his elementary education at the Elementary School in Baghdad until the age of 13 and then at the Government Public School in Baghdad until the age of 16. When his admission to the Government Secondary School was denied because of his Jewish faith, he moved to Basrah in 1940 and later returned to Baghdad to study in a private school for his last secondary school year. In 1941, at 18 years of age, he passed the secondary (baccalaureate) examination with excellent credentials. After completing his secondary education, he left Iraq to study philosophy and economics at the American University of Beirut (A.U.B.). In 1942, as a Goldberg scholar, Prof. Digital Object Identifier 10.1109/MCS.2009.935223

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Jury left Beirut to study electrical engineering at the Hebrew Technical College (now Technion—Israel Institute of Technology) at Haifa, in what was then Palestine. In 1947, immediately after receiving his diplome engineer degree in electrical engineering from the Technion, Prof. Jury made one of the most critical decisions of his career.

AT HARVARD AND COLUMBIA 1947–1954 Although he intended to pursue his graduate studies at Cambridge University in the United Kingdom, Prof. Jury chose Harvard University in the United States instead. To quote Prof. Jury [1], he arrived in the United States on November 1, 1947, in a situation quite different from those for whom, some 50 years earlier, the poet Emma Lazarus had written the sonnet inscribed on the Statue of Liberty, “Give me your tired, your poor, your huddled masses yearning to breathe free; the wretched refuse of your teeming shore. Send these, the homeless, the tempest-tost to me, I lift my lamp beside the golden door.” As with most young intellectuals who came to these shores as part of an influx of immigrants, it was the post-war renaissance and the observation that scientific and technical innovations were moving from Europe to America that primarily influenced his decision to choose Harvard over Cambridge. This decision led to an enduring impact on the broad area of discrete-time systems. In 1949, Prof. Jury obtained the M.S. degree from Harvard, which was the last M.S. awarded by its engineering school. Prof. Jury then moved to New York to attend Columbia University for his doctoral studies as a Higgins fellow. In 1953, he obtained the Sc.D. degree in electrical engineering from Columbia. On the occasion of Columbia’s Electrical Engineering Department’s centennial in May 1992, it was noted that the Sc.D. degree awarded to Prof. Jury was the first one presented at Columbia. As Prof. Jury recalls in [1], it was by a “stroke of fate” that two of his closest colleagues and friends, Prof. Faz Reza and Prof. Lotfi Zadeh, also arrived in the United States during the 1940s, attended Columbia University, albeit during different time periods, and studied and conducted research in closely related areas. Prof. Jury’s doctoral research supervisor was the late John Ralph Ragazzini who, along with his colleagues, is often credited with formally proposing the operational 1066-033X/10/$26.00©2010IEEE

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amplifier in 1945 [2]. The operational amplifier, or op-amp as it became popularly known, is now an indispensable building block in all electronic circuits. When Prof. Jury joined Columbia, three topics in control-related research were in vogue, the describing function, the phase plane, and sampled-data systems. Prof. Jury chose the last topic for his research mainly because it appeared to need the most work. In fact, he could find only two references related to this topic. The first reference was Chapter 5 of [3], a book from the M.I.T. Radiation Laboratory Series. The author, Witold Hurewicz, introduced the notation z for eTs. The second reference was a chapter on sampling written by George Stibitz, which appeared in a book by McCall of Bell Laboratories. This chapter introduced the “infinite summation” model of a sampler. The 1949 dissertation “Analysis and Design of Sampled-Data Control Systems” by William (Bill) K. Linvill at MIT was based on this model of the sampler, although Linvill was unaware of Stibitz’s work. To top it all off, Bill Linvill opted to use the notation z to denote e 2Ts (instead of eTs ). As Prof. Jury states in [1], “In those days, the M.I.T. researchers refer or read only M.I.T. publications!” Bill Linville’s 1949 dissertation, followed by Prof. Jury’s 1953 dissertation “Analysis and Synthesis of Sampled-Data Control Systems,” are quite probably the first documents that deal with the synthesis of sampled-data feedback systems. The 1950s and 1960s are fondly remembered as the golden era of systems and control theory for good reasons [2]. This phrase was likely coined by Tom Stern, who was chairman of Columbia’s Electrical Engineering Department in 1972–1974 and 1991–1993. During these two decades, several pioneering contributors to control graduated under the tutelage of John Ragazzini, including James Mulligan, Ralph Schwartz, Lotfi Zadeh (1949), Eli Jury (1953), Gene Franklin (1955), Jack Bertram, Bernard Friedland (1957), Herb Freeman, Jack Sklansky, Art Bergen, and Rudolf Kalman (1958). In 1979, in honor of John Ragazzini, the American Automatic Control Council (AACC) established the John R. Ragazzini Award to be “given to recognize outstanding contributions to automatic control education in any form.” Much of the analytical groundwork for sampled-data and discrete-time systems was determined by these trailblazers. The z-transform, under this same name, was introduced in [4] by John Ragazzini and Lotfi Zadeh in 1952; its use as a basic tool in discrete-time systems, especially in digital control systems and digital signal processing, along with the development of the modified z-transform, were the focus of Prof. Jury’s Sc.D. dissertation and book Sampled-Data Control Systems [5].

a professor in 1964, a position he held until June 30, 1981 (Figure 1). Prof. Jury refers to the 28 years (1954–1981) he spent at Berkeley as the “breakthrough in [his] academic career” [1]. Relishing in Berkeley’s academic environment and its tradition of facilitating faculty in the freedom to pursue research, Prof. Jury flourished and produced some of the most groundbreaking contributions in discrete-time systems and control. Prof. Jury identifies several factors that attributed to his productivity at Berkeley. The interaction he had with an amazing group of colleagues was surely one factor. Among these colleagues were Bergen, Desoer, Hopkin, Smith, Takahashi, and his long-time friend Zadeh, who had also joined Berkeley. The relationship between Prof. Jury and Prof. Zadeh is particularly warm and special. Prof. Jury was actually a student in the network theory course taught by Prof. Zadeh at Columbia, and they remain close professional colleagues and family friends. Prof. Jury also established collaborations with colleagues from other departments, notably the late Larry Stark who held appointments in the School of Optometry and departments of electrical engineering and computer science and mechanical engineering. Prof. Jury also benefited from his interaction and collaboration with internationally renowned scholars whom he met while they were visiting the university. Notable among these are Brian D.O. Anderson, Karl Astrom, Tom Bickart, Nirmal K. Bose, E.J. Davison, Rue Di Figuerido, Thomas Kailath, Mohamed Mansour, and S.K. Mitra. Prof. Jury considers the group of excellent and talented graduate students he has worked with throughout his career as the primary reason for his contributions. Starting as their doctoral research advisor, and then coauthor, he derives great pleasure and pride in identifying his former students as close personal friends. His interactions with his graduate students have always been to educate himself, as much if not more than how the students perceive him as their teacher. When Chi-Tsong Chen once asked what Prof.

AT BERKELEY 1954–1981 After receiving the Sc.D. degree, Prof. Jury stayed for six months at Columbia’s Electronic Research Laboratory (ERL). In 1954, he joined the University of California at Berkeley as an instructor in the Department of Electrical Engineering and Computer Sciences (EECS). He was appointed

FIGURE 1 Eliahu Jury at the University of California at Berkeley. FEBRUARY 2010

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Jury would like to be remembered by, it was not surprising that he responded, “lifetime graduate student.” Regarding this statement, in [1], Prof. Jury emphasizes, “this is indeed how I consider myself, for otherwise, my professional career will be obsolete and probably very limited.” Among his contributions during his years at Berkeley, three items stand out, namely, the Jury stability table, his authoritative book Theory and Application of the z-Transform Method [6], and the theory of inners. The Jury stability table makes it possible to study root distribution of a polynomial with respect to the unit circle in the complex plane without explicitly solving for the roots. This stability table is the discrete-time analog of the celebrated Routh table and the discrete-time counterpart of the Hurwitz criterion, which can be used to determine the root distribution with respect to the imaginary axis in the complex plane, again without solving for the roots explicitly. The original stability table that appeared in [7] has been refined, expanded, and generalized over the years, including applications to the stability of two-dimensional (2-D) and m-D discrete-time polynomials. It is certainly true that, with the advent and pervasiveness of digital computers, the use of tabular methods for determining root distribution (including Jury and Routh-Hurwitz tables) is not as widespread and popular

FIGURE 2 The July 1975 cover of the Proceedings of the IEEE was dedicated to inners. 74 IEEE CONTROL SYSTEMS MAGAZINE

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as it once was. However, the strength of tabular methods lies in their ability to handle symbolic expressions, thereby determining the ranges of the parameters for which the polynomial is stable and making them useful for stability determination of 2-D and m-D polynomials. Theory and Application of the z -Transform Method is quite possibly the most comprehensive and authoritative treatise written on the z -transform. It is a book that has had an enormous influence on the general area of discretetime systems and in particular, as the book’s title implies, on the theory and application of the z -transform in discrete-time systems. The theory of inners unifies the treatment of both continuous-time and discrete-time systems by combining the treatment of stability, root distribution, controllability, observability, and aperiodicity [8]. The July 1975 cover of the Proceedings of the IEEE reflects this utility (Figure 2). Prof. Jury’s third book Inners and Stability of Dynamic Systems [9] develops these ideas in detail. Prof. Jury takes special pride in two lectures he delivered. The first was the Routh Centennial Lecture at the occasion of the centennial of Routh’s famous Adams Prize Essay of 1877 [10]. By 1977, the seminal nature of Prof. Jury’s work had already been established, and the Routh Centennial Lecture was the “icing on the cake.” The second lecture was in 1995, when he delivered the Hurwitz Centennial Lecture during a workshop held in honor of Hurwitz at the ETH; the text of this lecture appears in [11]. Among the colleagues that he met or corresponded with while at Berkeley, Prof. Jury valued his close and personal relationship with Prof. Yakov Z. Tsypkin the most (Figure 3). A letter that Prof. Jury received from Tsypkin in April 1958, which in [1] he refers to as “an important event [that] brought great satisfaction and benefit,” led to correspondence that lasted for nearly four decades until the untimely death of Prof. Tsypkin in 1997. With an award in the distinguished professor category as a Fulbright-Hayes Fellow at the Kiev Polytechnic Institute, Prof. Jury also had the opportunity to collaborate with Prof. Tsypkin in person. While the research work on sampled-data systems in the West was mainly motivated by radar tracking systems that were being developed during World War II, in the then U.S.S.R., based on his own work on relay control systems, Tsypkin was also working on sampled-data systems. For this reason, Prof. Jury liked to refer to Prof. Tsypkin as the “father of sampled-data systems in the East.” I still remember how deeply affected Prof. Jury was on the day that he heard of Prof. Tsypkin’s passing away. I know how much they enjoyed the professional and personal relationship they, and their spouses, had developed over time. I was personally involved in gathering their correspondence and creating four bound volumes for the periods 1958–1968, 1968–1978, 1978–1988, and 1988–1997. One copy of these volumes is located in the Department of Electrical and Computer Engineering at the University of Miami; another copy is located at the Institute of Control Sciences at

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the Russian Academy of Sciences in Moscow, Russia, where Prof. Tsypkin was a member (or academician) at the time of his passing. When you read Prof. Jury’s memorial article for Prof. Tsypkin in [12], the respect and admiration that Prof. Jury had for Prof. Tsypkin is quite evident.

AT MIAMI 1981–PRESENT He was still at the peak of his professional career when, at the age of 58 years, Prof. Jury and his family moved to Miami in 1981. Primarily due to family health reasons, they were looking for a location on the sea coast, and Miami Beach fit the bill perfectly. After settling down in Miami Beach, one day Prof. Jury simply walked into the Department of Electrical and Computer Engineering at the University of Miami (UM) in Coral Gables, Florida. I am certain nobody had any inkling that this pioneer in control systems would be making an unannounced visit seeking employment. Of course, UM did not pass up this golden opportunity to add him to its faculty roster. So in July 1981, with the designation of professor emeritus of the University of California, Berkeley, Prof. Jury joined UM’s Department of Electrical and Computer Engineering as a research professor (Figure 4). His research output continued unabated while at Miami. Among the research contributions he made during this time, his impact on two areas have been highly influential. The first area involves 2-D and m-D discrete-time systems. Of course, he was already well known for several contributions in this research area, as evident from the preface he wrote for a special issue on multidimensional systems in the Proceedings of the IEEE [13]. At Miami, he continued his work on 2-D and m-D systems, in particular, on issues related to their stability and model reduction [14]. The second area of research that Prof. Jury pursued focused on stability issues related to interval polynomials. Robust stability of interval polynomials was a completely new research topic that was engendered by one amazing result by the Russian researcher V.L. Kharitonov on the stability of interval polynomials with respect to the imaginary axis in the complex plane. Prof. Jury made significant contributions, especially regarding stability of interval polynomials with respect to the unit circle in the complex plane. During his tenure at Miami, Prof. Jury continued to collaborate with various colleagues. In particular, he collaborated with two researchers that he had initially established contact with while he was at Berkeley, Mohamed Mansour, who was then the head of the Institut für Automatik (Automatic Control Laboratory) of the Eidgenössische Technische Hochschule (ETH), or the Swiss Federal Institute of Technology, in Zürich, and Brian D.O. Anderson, who was then the head of the Department of Systems Engineering at the Australian National University (ANC) in Canberra. Prof. Jury spent many summers at the ETH working with Prof. Mansour and Prof. Anderson. This collaboration, which lasted for more than a decade, was extremely fruitful and produced results in a variety of research topics, including

FIGURE 3 Eliahu Jury (left) and Yakov Tsypkin (right) at the First IFAC World Congress in Moscow, 1960.

2-D and m-D discrete-time systems, model reduction, and robust stability. Another activity Prof. Jury enjoyed and absorbed himself in was contacts with colleagues at his alma mater, the Technion. He has particularly enjoyed his relationship with Ezra Zeheb, who was then a faculty member in the Department of Electrical Engineering. Prof. Jury also re-established contact with Shaul Gutman, a former student from Berkeley now affiliated with the Technion’s Department of Mechanical Engineering. Mindful of and in gratitude toward the students who had been a constant inspiration throughout his career, Prof. Jury established undergraduate and graduate student awards at the five academic institutions that had a major influence on him, the Technion, Harvard, Columbia, Berkeley, and Miami. At Miami, he established the Eliahu I. and Joyce Jury Seminar and Awards, which has now become an annual departmental tradition where, accompanied by a seminar presentation by a leading researcher, the best and the brightest of the department’s graduate and undergraduate students are honored. Over the years, some of the most influential researchers in control-related areas have visited Miami to deliver the Jury

FIGURE 4 Eliahu Jury at the University of Miami. FEBRUARY 2010

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FIGURE 5 Yakov Tsypkin’s visit to the University of Miami to deliver the 1989 Jury Lecture. Yakov Tsypkin is on the right. The cabinet in the background contains Eliahu Jury’s medals and honors, which he donated to the University of Miami.

Lecture. Indeed, the list of previous Jury Lecture presenters includes Anderson, Astrom, Bose, Jamshidi, Kailath, Mansour, Tsypkin (Figure 5), and Zadeh. Prof. Jury established a similar annual Jury Lecture at the Technion as well. Prof. Jury has always been a keen follower of the history of science. He has great admiration and respect for those scientists who paved the way for the next generation of researchers. This respect is evident from his article on the stability theory pioneers Hermite, Routh, Lyapunov, and Hurwitz [15]. After retiring from Miami in 1988, he became an avid reader of articles and books on historical events and has written on the history of science (see, for example, [16]). Prof. Jury has an incredible memory for detail. Even now, when I cannot locate a lesser known article, I call him and he invariably “narrows down” the search for me. So, with years and dates of events, conferences, and meetings with colleagues easily flowing, it is easy for him to carry on a pleasant and more “personalized” conversation with anyone. You can imagine how comforting this is for a young faculty member who has just met a pioneering researcher in their field. In 1996, after reading the autobiography of Sir Hermann Bondi [17], Prof. Jury realized that events in his own life story had parallels to Sir Bondi’s life. Sir Bondi is the famous

FIGURE 6 Prof. Sir Hermann Bondi’s visit to the University of Miami to deliver the 1997 Jury Lecture. From left: Sir Bondi, Eliahu Jury, Kamal Yacoub, and Tzay Young. 76 IEEE CONTROL SYSTEMS MAGAZINE

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British astrophysicist and cosmologist who, together with Thomas Gold and Fred Hoyle, developed and proposed the steady-state theory of the universe. Writing to Sir Bondi, Prof. Jury began a string of correspondence that developed into a close and warm friendship until Sir Bondi’s passing in 2005. Lady Bondi has recently given this correspondence between Bondi and Prof. Jury to the Archives Centre of the Churchill College, University of Cambridge, United Kingdom In fact, Sir Bondi delivered the Jury Lecture at Miami in 1997 (Figure 6). I hosted Sir Bondi during his visit to Miami, and I derived enormous pleasure in the conversations I had with this incredible scientist. At the conclusion of his visit, Sir Bondi graciously invited me to visit him at Churchill College, an opportunity of which I took advantage.

TO CONCLUDE. . . Prof. Jury’s research contributions in systems and control have been influential, pioneering, and often seminal. Several generations of young students who have gone on to pursue careers in academia, industry, and government have benefitted from Prof. Jury’s mentorship and close friendship. The roughly 50 M.S. students and 30 Ph.D. students who have graduated under Prof. Jury’s supervision can certainly attest to this. In 1991, a conference was organized in recognition of Prof. Jury’s contributions and in appreciation of his interest in and generosity toward the education of talented students. The proceedings of this conference appears in [1]. For his research contributions and his dedication to education, Prof. Jury has received awards that are too numerous to mention. However, I must mention some of the more prestigious awards, including the ASME Centennial Medal (1980), Honorary Doctor of Science Degree from the ETH (1982), the first Education Award of the IEEE Circuits and Systems Society (1986), the Rufus Oldenberger Award of the American Society of Mechanical Engineers (1986), the first Distinguished Faculty Scholar Award of the University of Miami (1988), the Technion Founders’ Award (1990), the Phoebe Apperson Heart Medal from the University of California at Berkeley (1991), the University of Rome Medal (1992), the Egleston Medal of the Columbia University Engineering School Alumni Association (1999), the Golden Jubilee Medal of the IEEE Circuits and Systems Society (1999), the IEEE Millennium Medal (2000), the Honorary Fellow Degree from the Technion (2001), and the Heaviside Premium (2002) from the IEE (now IET). Prof. Jury donated the many medals and awards he received throughout his career to the University of Miami. I was personally involved in having his publications bound into seven volumes, each volume (except the first one, which spans the 15 years of 1954–1968) spanning a fiveyear period of Prof. Jury’s career. These bound volumes and copies of all his books (including translations in several languages) as well as his medals and awards remain on display at the Department of Electrical and Computer Engineering in the University of Miami. The ETH and the

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Tel Aviv University in Israel also carry a complete set of Prof. Jury’s publication volumes. I wish to conclude this article by relating several pieces of advice that Prof. Jury likes to offer to students and colleagues: 1) Do not be overly disappointed if an otherwise novel idea or method does not attract the attention of the wider research community. Such ideas, if they are sufficiently important, may resurface and catch the attention of others with the advent of new technology and other techniques. 2) Do not get too upset if a research idea does not get the recognition that you feel it deserves. Important and pioneering work will shine even if the corresponding article appeared in an obscure journal as a short note. 3) Research results toward which a significant effort was expended may not get as much recognition as a result that was simpler and easier to derive. In other words, do not judge your work by the time and effort invested in it; let the peer community make its own judgment and evaluation in its own time. 4) Do not assume that research approaches, methods, and ideas can be “monopolized.” It is often the case that other researchers have independently arrived at the same, or quite similar, results. 5) No research idea can remain dominant over the longer period of time. Progress in science inevitably generates new and better ideas. During research meetings that Prof. Jury had with Peter Bauer (now at the University of Notre Dame) and myself in Miami Beach, one piece of advice he gave us is worth repeating: “Pounding your head against the wall for hours is not the way to crack a hard problem. Instead, change the environment, take a break, take a walk around the lake or on the beach. And then come back to the problem.” Prof. Jury also liked to quote Ludwig Boltzmann in response to those who criticize purely theoretical contributions: “Gute theorie ist beste praxis,” which translates to “Good theory is best practice.” Finally, let me quote a paragraph from a tribute that Lotfi Zadeh gave in 1999 at the occasion of presenting the Egleston Award of Columbia University Engineering School Alumni Association: Prof. Jury is more than a man of science and intellectual pursuits. He is an extremely kind and generous person, loved by all who know him. He is a true scholar and a role model for his students, many of whom have achieved prominence in their fields. I should like to pay tribute to [him], a deep thinker, a dedicated scholar, a man of ideals and impeccable integrity . . .

ACKNOWLEDGMENTS The author appreciates the assistance and suggestions of Eyad H. Abed of the University of Maryland, Peter

H. Bauer of the University of Notre Dame, and Reuven Lask and Manohar N. Murthi of the University of Miami. Photos are courtesy of Prof. Jury.

AUTHOR INFORMATION Kamal Premaratne ([email protected]) received the B.Sc. in 1982 from University of Moratuwa, Sri Lanka. He obtained the M.S. and Ph.D. under Eliahu Jury’s supervision, in 1984 and 1988, respectively, from the University of Miami, Coral Gables, Florida, where he is presently a professor in the Department of Electrical and Computer Engineering. He received the 1992/1993 Mather Premium and the 1999/2000 Heaviside Premium of the Institution of Electrical Engineers. He has served as an associate editor of IEEE Transactions on Signal Processing and the Journal of the Franklin Institute. He is a Fellow of IET (formerly IEE). His research interests include evidence fusion and resource management in distributed decision and sensor networks, knowledge discovery from imperfect data, and network congestion control.

REFERENCES [1] E. I. Jury, “Reflections on four decades of an academic career,” in Fundamentals of Discrete-Time Systems: A Tribute to Professor Eliahu I. Jury, M. Jamshidi, M. Mansour, B. D. O. Anderson, and N. K. Bose, Eds. Albuquerque, NM: TSI Press, 1994, pp. 3–8. [2] Columbia University Electrical Engineering History. Postwar period: The golden era of systems and control theory. Columbia University, The Fu Foundation School of Engineering and Applied Science, Electrical Engineering Department. [Online]. Available: www.ee.columbia.edu/pages/ deptoverview/history/index.html [3] W. Hurewicz, “Filters and servosystems with pulsed data,” in Theory of Servomachanism, (Massachusetts Institute of Technology Radiation Laboratory Series), H. J. James, N. B. Nichols, and R. S. Phillips, Eds. New York, NY: McGraw-Hill, 1947, pp. 231–261. [4] J. R. Ragazzini and L. A. Zadeh, “The analysis of sampled-data systems,” Trans. Amer. Inst. Electr. Eng., vol. 1, no. 3, pp. 225–234, Nov. 1952. [5] E. I. Jury, Sampled-Data Control Systems. New York, NY: Wiley, 1958. [6] E. I. Jury, Theory and Application of the z -Transform Method. Malabar, FL: Robert E. Krieger, 1964. [7] E. I. Jury, “A simplified stability criterion for linear discrete systems,” Univ. California, Berkeley, CA, Tech. Rep. ERL Report #60-373, June 1961. [8] E. I. Jury, “The theory and application of the inners,” Proc. IEEE, vol. 63, no. 7, pp. 1044–1068, July 1975. [9] E. I. Jury, Inners and Stability of Dynamic Systems. New York: Wiley, 1974. [10] E. I. Jury, “Stability tests for one, two, and multidimensional linear systems,” Proc. Inst. Electr. Eng., vol. 124, no. 12, pp. 1237–1240, Dec. 1977. [11] E. I. Jury, “From J. J. Sylvester to Adolf Hurwitz: a historical review,” in Stability Theory, Hurwitz Centenary Conf. (International Series of Numerical Mathematics), R. Jeltsch and M. Mansour, Eds. New York: Springer-Verlag, 1996, vol. 121, pp. 53–65. [12] E. I. Jury, “In memoriam—Yakov Zalmanovitch Tsypkin: A life in feedback control,” IEEE Trans. Automat. Contr., vol. 43, no. 4, pp. 455–456, Apr. 1998. [13] E. I. Jury,, “Preface to the special issue on multidimensional systems,” Proc. IEEE, vol. 65, no. 6, pp. 822–823, June 1977. [14] E. I. Jury, “Stability of multidimensional systems and related problems,” in Multidimensional Systems: Techniques and Applications, S. G. Tzafestas, Ed. New York: Marcel Dekker, 1986. [15] E. I. Jury, “Remembering four stability theory pioneers of the nineteenth century,” IEEE Trans. Circuits Syst. I: Fundamental Theory Appl., vol. 43, no. 10, pp. 821–823, Oct. 1996. [16] E. I. Jury, “The roles of Sylvester and Bezoutian matrices in the historical study of stability of linear discrete-time systems,” IEEE Trans. Circuits Syst. I: Fundamental Theory Appl., vol. 45, no. 12, pp. 1233–1251, Dec. 1998. [17] H. Bondi, Science, Churchill, and Me: The Autobiography of Hermann Bondi, Master of Churchill College, Cambridge. Tarrytown, NY: Pergamon Press, 1990.

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