International yearbook of education, Vol. XXIII, 1961. 

 - Geneva :  Paris :  IBE,  UNESCO,  1962. 
 - 500 p. 
 - IBE publication ;  236. .
<br/><br/><label>No. de Clasificación Universal Decimal: </label>OC 37 (100) =20 "1961" INN Vol. 23