TY  - JOUR
AU  - L. A. Sakhnovich
TI  - Necessary conditions for the existence of a~transformation operator for fourth-order equations
JO  - Trudy Matematicheskogo Instituta imeni V.A. Steklova
PY  - 1961
VL  - 16
IS  - 5
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/RM_1961_16_5_a13/
LA  - ru
ID  - RM_1961_16_5_a13
ER  -