Worldwatch paper. 

 - Washington, D.C. :  Worldwatch Institute,  1975-2006 
 - No. 1 (1975) - No. 172 (2006) 
 - Irregular 
<br/><br/><label>Subjects--Topical Terms: </label><br/>RECURSOS NATURALES
<br/><br/><label>Index Terms--Genre/Form: </label><br/>PUBLICACIONES PERIODICAS