Partial Differential Equations - Fritz John - Bog

From the reviews of the earlier editions:
¿An excellent second-reading text. Should be accessible to any mathematician. Highly recommended.¿ ¿ The Mathematical Gazette

¿An excellent text upon which to build and introduction to partial differential equations at the graduate level. In addition¿recommended for the nonspecialist.¿ ¿ American Mathematical Monthly

Partial Differential Equations is a very well accepted introduction to the subject. In it, the author identifies the significant aspects of the theory and explores them with a limited amount of machinery from mathematical analysis. Now, in this fourth edition, the book has again been updated with an additional chapter on Lewy¿s example of a linear equation with solutions.