This volume is dedicated to the memory of Potapov, who made important contributions in the areas of operator theory, complex analysis and their points of juncture. The book commences with biographical material, and then presents a collection of papers on different aspects of operator theory and complex analysis covering the achievements of the Odessa-Kharkov school, of which Potapov was a member. The papers deal with interrelated problems and methods. The main topics are the multiplicative structure of contractive matrix and operator functions, operators in spaces with indefinite scalar products, inverse problems for systems of differential equations, interpolation and approximation problems for operator and matrix functions. This book should be suitable for mathematicians and engineers.