This book is a tribute to Professor Jindrich Nečas on the occasion of his 70th birthday. It contains 61 refereed contributions from mathematicians in 11 countries, covering various areas related to Nečas's work, including Navier-Stokes equations, nonlinear elasticity, non-Newtonian fluids, regularity of solutions of parabolic and elliptic problems, operator theory, and numerical methods. The book was made possible by the support of the Centro de Matemática Aplicada (CMA/IST) and the Fundação Calouste Gulbenkian. The editors express their gratitude to Dr. Oldřich Ulych for his help in preparing the final version of the book and to Dr. Šárka Matušů-Nečasová for her support. Nečas is a distinguished mathematician who has made significant contributions to partial differential equations, nonlinear functional analysis, and their applications in continuum mechanics and hydrodynamics. He has been a professor at Charles University in Prague and has held various academic positions in the Czech Republic and abroad. He has also been a mentor to many students and has organized numerous academic events, including Summer Schools on nonlinear partial differential equations and Navier-Stokes equations. Nečas's work includes the development of the theory of nonlinear elliptic equations, the study of regularity of solutions to partial differential equations, and the analysis of nonlinear operators. He has also contributed to the study of continuum mechanics, including the mechanics of elastoplastic bodies and the theory of multipolar fluids. His research has had a significant impact on the development of mathematical analysis and its applications in various fields. The book includes a list of Nečas's most significant works, including monographs and papers that highlight his contributions to mathematics. The book also features contributions from other mathematicians who have been influenced by Nečas's work. The contributions cover a wide range of topics, including the regularity of solutions to partial differential equations, the study of nonlinear operators, and the analysis of fluid dynamics. The book is a tribute to Nečas's contributions to mathematics and a celebration of his legacy.This book is a tribute to Professor Jindrich Nečas on the occasion of his 70th birthday. It contains 61 refereed contributions from mathematicians in 11 countries, covering various areas related to Nečas's work, including Navier-Stokes equations, nonlinear elasticity, non-Newtonian fluids, regularity of solutions of parabolic and elliptic problems, operator theory, and numerical methods. The book was made possible by the support of the Centro de Matemática Aplicada (CMA/IST) and the Fundação Calouste Gulbenkian. The editors express their gratitude to Dr. Oldřich Ulych for his help in preparing the final version of the book and to Dr. Šárka Matušů-Nečasová for her support. Nečas is a distinguished mathematician who has made significant contributions to partial differential equations, nonlinear functional analysis, and their applications in continuum mechanics and hydrodynamics. He has been a professor at Charles University in Prague and has held various academic positions in the Czech Republic and abroad. He has also been a mentor to many students and has organized numerous academic events, including Summer Schools on nonlinear partial differential equations and Navier-Stokes equations. Nečas's work includes the development of the theory of nonlinear elliptic equations, the study of regularity of solutions to partial differential equations, and the analysis of nonlinear operators. He has also contributed to the study of continuum mechanics, including the mechanics of elastoplastic bodies and the theory of multipolar fluids. His research has had a significant impact on the development of mathematical analysis and its applications in various fields. The book includes a list of Nečas's most significant works, including monographs and papers that highlight his contributions to mathematics. The book also features contributions from other mathematicians who have been influenced by Nečas's work. The contributions cover a wide range of topics, including the regularity of solutions to partial differential equations, the study of nonlinear operators, and the analysis of fluid dynamics. The book is a tribute to Nečas's contributions to mathematics and a celebration of his legacy.