00357nam a2200121Ia 4500082002100000100002200021245004800043260003500091300002900126490007000155500000500225700000500230  a515.35bSc314.SP  aSchechter, Martin  aSpectra of partial differential operatorsb  aAmsterdambNorth-Hollandc1971  axiii, 267p. Index, Bibl.  aNorth-Holland series in Applied Mathematics and mechanicsv v. 14  a  a