Education clearing houses and documentation centres :  A preliminary international survey. 

 - Paris :  UNESCO,  1957. 
 - 65 p. 
 - Educational studies and documents ;  22. .
<br/><br/><label>No. de Clasificación Universal Decimal: </label>OC 058.7: 002.6: 37.001.5 (100) =20 CEN No.22.