This book by two of the foremost researchers and writers in the field is the first part of a treatise that covers the subject in breadth and depth, paying special attention to the historical origins of the theory. Both individually and collectively these volumes have already become standard references.

Applications-oriented introduction to variational theory develops insight and promotes understanding of specialized books and research papers. Suitable for advanced undergraduate and graduate students as a primary or supplementary text. 1969 edition.

Matrix algebra has been called "the arithmetic of higher mathematics" [Be]. We think the basis for a better arithmetic has long been available, but its versatility has hardly been appreciated, and it has not yet been integrated into the mainstream of mathematics. We refer to the system commonly called 'Clifford Algebra', though we prefer the name 'Geometric Algebm' suggested by Clifford himself. Many distinct algebraic systems have been adapted or developed to express geometric relations and describe geometric structures. Especially notable are those algebras which have been used for this purpose in physics, in particular, the system of complex numbers, the quatemions, matrix algebra, vector, tensor and spinor algebras and the algebra of differential forms. Each of these geometric algebras has some significant advantage over the others in certain applications, so no one of them provides an adequate algebraic structure for all purposes of geometry and physics. At the same time, the algebras overlap considerably, so they provide several different mathematical representations for individual geometrical or physical ideas.

Quadratic variational theory; Stochastic functional equations: continuity properties and relation to ordinary equations; Partial regularity theorems for elliptic systems; Strengthening caratheodory's method to apply in control problems; Optimal control problems as mathematical programming in an unorthodox function space; Controlled diffusions under polynomial growth conditions; Separation and support properties of convex sets - a survey; Some non-classical variational problems arising from optimal filter problems; A new existence theorem in the class of piecewise continuous control functions; The epsilon technique - a constructive approach to optimal control; Lagrange multipliers re-visited.

Although finite elasticity theory has its roots in the nineteenth century, its development was largely neglected until the end of the Second World War. Since then it has attracted a substantial amount of attention and considerable progress has been made both in our understanding of the basis of the subject and in its applications. It occurred to me about three years ago that finite elasticity had reached a level of development at which an international symposium on the subject was overdue. Accordingly, with strong encouragement from Professor P. M. Naghdi and numerous other colleagues, I submitted to the International Union of Theoretical and Applied Mechanics a proposal for their support of such a symposium to be held at Lehigh University during the period August 10-15, 1980. The proposal received enthusiastic support from the International Union and an international scientific committee under my chairmanship, consisting of Professors G. Fichera (Rome), W. T. Koiter (Delft), L. I. Sedov (Moscow), and A. J. M. Spencer (Nottingham), was assigned responsibility for the scientific program. In constructing the program we aimed at as broad a coverage as possible of the many aspects of the subject on which significant progress is currently being made. These range from theoretical studies of existence and uniqueness of solutions of the governing equations of finite elasticity theory to experimental studies of its application to such problems as tear resistance and friction in vulcanized rubbers.

These notes are the result of an interrupted sequence of seminars on optimiza tion theory with economic applications starting in 1964-1965. This is mentioned by way of explaining the uneven style that pervades them. Lately I have been using the notes for a two semester course on the subject for graduate students in economics. Except for the introductory survey, the notes are intended to provide an appetizer to more sophisticated aspects of optimization theory and economic theory. The notes are divided into three parts. Part I collects most of the results on constrained extremf! of differentiable functionals on finite and not so finite dimensional spaces. It is to be used as a reference and as a place to find credits to various authors whose ideas we report. Part II is concerned with finite dimensional problems and is written in detail. Needless to say, my contributions are marginal. The economic examples are well known and are presented by way of illustrating the theory. Part III is devoted to variational problems leading to a discussion of some optimal control problems. There is a vast amount of literature on these problems and I tried to limit my intrusions to explaining some of the obvious steps that are usually left out. I have borrowed heavily from Akhiezer [ 1], Berkovitz [ 7], Bliss [lOJ and Pars [40J. The economic applications represent some of my work and are presented in the spirit of illustration.

In this book, we study theoretical and practical aspects of computing methods for mathematical modelling of nonlinear systems. A number of computing techniques are considered, such as methods of operator approximation with any given accuracy; operator interpolation techniques including a non-Lagrange interpolation; methods of system representation subject to constraints associated with concepts of causality, memory and stationarity; methods of system representation with an accuracy that is the best within a given class of models; methods of covariance matrix estimation;methods for low-rank matrix approximations; hybrid methods based on a combination of iterative procedures and best operator approximation; andmethods for information compression and filtering under condition that a filter model should satisfy restrictions associated with causality and different types of memory.As a result, the book represents a blend of new methods in general computational analysis,and specific, but also generic, techniques for study of systems theory ant its particularbranches, such as optimal filtering and information compression.- Best operator approximation,- Non-Lagrange interpolation,- Generic Karhunen-Loeve transform- Generalised low-rank matrix approximation- Optimal data compression- Optimal nonlinear filtering