Ball, Derek. <br/><br/>
Forty harder problems for the classroom / 
by derek Ball. 
 - Derby :  Associatin of Teachers of Mathematics,  2005. 
 - 28 p. : ;  27 cm. 
<br/><br/><label>ISBN: </label>1898611327 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Mathematics--Problems, etc.<br/>Mathematics--Study and teaching.