TY  - BOOK
AU  - Oleinik O A
AU  -  Radkevic E V
TI  - Second order equations with nonnegative characteristic form
U1  - B334,7,2:7, L3 
PY  - 1973///
CY  - New York    
PB  -  American Mathematical Society      
KW  -  Boundary value problems
KW  - Differential equations
ER  -