TY  - BOOK
AU  - Elsgolts, L. E.
AU  - Yankovsky, George
TI  - Differential Equations and the Calculus of Variations 
U1  - 515.35 
PY  - 1970///
CY  - Moscow : 
PB  - Mir Publishers, 
KW  - Differential Equations
N1  - NN
ER  -