00358nam a2200121Ia 4500082002000000100003600020245004900056260003400105300002800139490003500167500000500202700002900207  a515.72bEd24.ST  aEdmunds, D. E. and Evans, W. D.  aSpectral theory and differential operatorsb  aOxfordbClarendon Pressc1989  axvi, 574p. Index, Bibl.  aOxford Mathematical monographs  a  aEvans, W. D. ; jt. auth.