TY  - BOOK
AU  - Gruber H E
AU  -  Voneche J J
AU  - `
ED  - `
TI  - Essential piaget :  an interpretive reference and guide
U1  - S1xM96, L7 
PY  - 1977///
CY  - LOndon
PB  - Routledge       
KW  - PSYCHOLOGY
ER  -