Differential equations : La Pietra 1996 : Conference on Differential Equations marking the 70th birthdays of Peter Lax and Louis Nirenberg, July 3-7, 1996, Villa La Pietra, Florence, Italy / - Lax, Peter D.; Nirenberg, L.; Giaquinta, Mariano,; Shatah, Jalal M. Ihsan,; Varadhan, S. R. S. (American Mathematical Society,, 1999)