TY  - JOUR
AU  - V. Yu. Popov
TI  - Direct and inverse inequalities for $\varphi$-Fej\'er mean-square approximations
JO  - Matematičeskie zametki
PY  - 1976
SP  - 353
EP  - 364
VL  - 19
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MZM_1976_19_3_a4/
LA  - ru
ID  - MZM_1976_19_3_a4
ER  -