The Organization of productive work in secondary technical and vocational education in the People's Republic of Bulgaria. 

 - Paris :  UNESCO,  1984. 
 - 17 p. 
 - ED-84/WS/43 .
<br/><br/><label>No. de Clasificación Universal Decimal: </label>373.62: 331 (497.2) =20ORG No.3.