This book contains the major works of Ivan Georgievich Petrowsky on systems of partial differential equations and algebraic geometry. The articles are of crucial importance for the topology of real algebraic manifolds and are the source of intensive development of theory of real algebraic manifolds.

Each of the articles is accompanied by the editor's notes. In addition, each article has been studied (and, in parts, corrected) by modern Russian mathematicians and appears with their commentaries.
This deals with the theory of systems of partial differential equations and is central to the modern general theory of such systems. It was in these works that the classes of elliptic, hyperbolic, and paranbolic systems were singled out and studied for the first time. These articles are at the origin of vast and important disciplines in the theory of partial differential equations and its applications.