TY  - BOOK
AU  - Donner Klaus
TI  - Extension of positive operators and korovkin theorems
T2  - Lecture notes in mathematics; 904
U1  - B48, M2 
PY  - 1982///
CY  - Berlin
PB  - Springer-Verlag         
KW  -  Operational
KW  - Positve operator
ER  -