TY  - BOOK
AU  - Butzer P L
AU  - Berens Hubert
TI  - Semi groups of operators and approximation
U1  - 512.724 
PY  - 1967///
CY  - Berlin
PB  - Springer Verlag
KW  - Approximations
KW  - Operator theory
KW  - Semi groups
ER  -