TY  - JOUR
AU  - A. Yu. Levin
AU  - G. D. Stepanov
TI  - One-dimensional boundary value problems with operators that do not lower the number of sign alternations
JO  - Trudy Matematicheskogo Instituta imeni V.A. Steklova
PY  - 1975
VL  - 30
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/RM_1975_30_1_a19/
LA  - ru
ID  - RM_1975_30_1_a19
ER  -