Biocenoses and agriculture in a semi-arid and gypseous environment of the Central Ebro Valley, Spain 
Juan Herrero (Ed.) 
 - Lleida  Universitat  D.L. 1996 
 - 21 p.  30 cm 
<br/><br/><label>Subjects--Index Terms: </label>Congresos Aragon Ciencia del suelo