2014 Reprint of 1963 Edition. Full facsimile of the original edition, not reproduced with Optical Recognition Software. Olga Aleksandrovna Ladyzhenskaya was a Soviet and Russian mathematician. She was known for her work on partial differential equations (especially Hilbert's 19th problem) and fluid dynamics. She provided the first rigorous proofs of the convergence of a finite difference method for the Navier-Stokes equations. This is a revised and updated edition of a book of fundamental importance in the rigorous theory of solutions of the Navier-Stokes equations. The author considers the...