The present volume is a sequel to that published in the series Springer Lecture Notes in Mathematics, as vol. 684, in 1978. During the last two years, a number of new results obtained by the author have contributed to the clarification of the general framework on which the previous volume was based, and have come to enrich and lift to a new level of generality the results published earlier. An attempt is made here to present these developments in a self-contained manner.
In developing the present method, the author's main concern has been to try to find a unified way of dealing with weak solutions of general nonlinear PDEs, a way which would exhibit a certain natural, objective trait, thus going beyond the somewhat adhoc appearance the customary functional analytic methods, with their wealth of linear topological structures and function spaces used, might now and then suggest.
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