TY  - JOUR
AU  - S. I. Novikov
TI  - Widths of a class of periodic functions defined by a differential operator
JO  - Matematičeskie zametki
PY  - 1987
SP  - 194
EP  - 206
VL  - 42
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MZM_1987_42_2_a3/
LA  - ru
ID  - MZM_1987_42_2_a3
ER  -