Introduction to logic 
Cruz, Corazon L. 
 - third edition. 
 -  National Book Store.  1993 
 - x, 357 pages. 
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<br/><br/><label>ISBN: </label>9-71085496-8 
<br/><br/><label>Dewey Class. No.: </label>F 160.914 C88i 1993