Opolya, George. <br/><br/>
Mathematical discorvery :  on understanding, learning, and teaching problem solving / 
Opolya, George. 
 - USA  John wiley & sons  1967 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Methametics
<br/><br/><label>Dewey Class. No.: </label>510  / POL