TY  - BOOK
AU  - Hellwig, Gunter
AU  - Hellwig, Birgitta, tr.
TI  - Differential operators of mathematical physics: an introduction
T2  - Addison-Wesley series in mathemtics
U1  - 515.724 
PY  - 1964///
CY  - London
PB  - Addison-Wesley
N1  - Includes bibliographical references and index
ER  -