Polya, G. <br/><br/>
How to solve it :  mathematical method.-2nd ed. 
G. Polya 
 - 2nd ed. 
 - New Delhi:  Prentice Hall of India,  2001. 
 - xxi, 253p. 
<br/><br/><label>Subjects--Index Terms: </label>Mathematical recreations. 
<br/><br/><label>Universal Decimal Class. No.: </label>51-8  / POL