TY  - BOOK
AU  - Hellwig, Gunter,
TI  - Differential operators of mathematical physics: An introduction 
AV  - QA432 H44
PY  - 1967///
CY  - Reading, mass.
PB  - Addison-Wesley
KW  - Cálculo operacional
KW  - Espacio de Hilbert
ER  -