TY  - JOUR
AU  - M. A. Krasnosel'skii
TI  - An alternative principle for the existence of periodic solutions for differential equations with retarded argument
JO  - Doklady Akademii Nauk
PY  - 1963
SP  - 801
EP  - 804
VL  - 152
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DAN_1963_152_4_a7/
LA  - ru
ID  - DAN_1963_152_4_a7
ER  -