TY  - BOOK
AU  - Hellwig,Günter
AU  - Gerlach,E.
TI  - Partial differential equations: an introduction 
AV  - QA374 .H45513 1964
PY  - 1964///
CY  - New York
PB  - Blaisdell
KW  - Differential equations, Partial
ER  -