The Analysis of Linear Partial Differential Operators II: Differential Operators with Constant Coefficients (Grundlehren Der Mathematischen Wissenschaften)

From the reviews: "With the basic theory of distributions and Fourier analysis set down, volume II proceeds deeper into the study of linear PDE, particularly with constant coefficients. Detailed analysis is made of the regularity of certain fundamental solutions of general constant coefficient operators P(D), including a classification of when P(D) is hypoelliptic." American Mathematical Monthly#1 "The books are very careful written. They give a good introduction into the areas considered. The reviewer's opinion is that L. Hörmander`s books will be a basis for studying differential equations for a long time." ZAMM#2