Introduction to logic 
Cruz, Corazon L. 
 - fourth edition. 
 -  National Book Store.  1995 
 - xii, 363 pages. 
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<br/><br/><label>ISBN: </label>9-71085797-5 
<br/><br/><label>Dewey Class. No.: </label>GS 160 C88i 1995