Hallerberg, Arthur E.,  1918-1978. <br/><br/>
Mathematical proof :  an elementary approach / 
by Arthur E. Hallerberg 
 - New York :  Hafner Press,  1974 
 - viii, 104 p. :  ill. ;  28 cm. 
<br/><br/><label>ISBN: </label>0028456904 
<br/><br/><label>LCCN: </label>72-094008 //r872 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Proof theory