TY  - BOOK
AU  - GOURSAT Edouard
AU  -  BERGMANN Howard G Tr.
TI  - Variation of solutions partial differential equations of the second order
T2  - A course in mathematical analysis;3
U1  - B334, K4/SC 
PY  - 1964///
CY  - New York
PB  - Dover publications        
ER  -