Address by Federico Mayor at the ceremony for presentation of the 1991 Sultan Qaboos Prizefor enviromental preservation :  beig awarded for the firts time. 

 - [Ginebra] :  UNESCO,  1991. 
 - 8 p. 
 - DG 91 ;  35 .
<br/><br/><label>Encabezamiento--Nombre Corporativo: </label><br/>Unesco