Sonford, Devid H. <br/><br/>
Ifp,Then G. Contitionels And The Foundations Of Reasoning 

 - London  Rontudge  1992 
 - 265 p. 
<br/><br/><label>ISBN: </label>0-415-07994-2 
<br/><br/><label>Dewey Class. No.: </label>160