TY  - BOOK
AU  - Sigel,Irving E.
TI  - Logical thinking in children : research based on Piaget's theory
U1  - 155.413 S574L 1968 
PY  - 1968///
CY  - New York : 
PB  - Holt Rinehart and winston press
KW  - Child psychology
KW  - Conservation of substance (Psychology)
N1  - Includes Index
ER  -