Gruber ,H .E  <br/><br/>
The Essential Piaget / 

 - London  Routledge and Kegan ltd  1977 
 - xlii, 881p; ill  hbk 
<br/><br/><label>ISBN: </label>071009213X 
<br/><br/><label>LC Class. No.: </label>BF723.E7 1977