@book{12556, author = {Symposium in Pure Mathematics, and Spencer, D. C. and American Mathematical Society.}, title = {Partial differential equations.}, publisher = {American Mathematical Society,}, year = {1973.}, address = {Providence,}, note = {"An outgrowth of lectures delivered at the eighteenth Summer Research Institute of the American Mathematical Society ... held ... from August 9 to August 27, 1971."} }