Ault, Ruth L. <br/><br/>
Children's cognitive development :  Piaget's theory and the process aproach / 
by Ruth L. Ault. 
 - New York :  Oxford University,  1977. 
 - 193 p. :  il. 
<br/><br/><label>Encabezamiento--Tema: </label><br/>Niņo, Estudio del