Economics : an introduction 
Villegas, Bernardo M. 
 - fourth edition. 
 -  Sinag-tala Publishers Inc.  1992 
 - 383 pages. 
<br/><br/>
<br/><br/><label>ISBN: </label>9-71117067-1 
<br/><br/><label>Dewey Class. No.: </label>F 330 V71e 1992