"Ruth Merttens and David  Kirkby" <br/><br/>
Abacus evolve  6 Text  book 2 

 - London  Pearson Education Limited  2007 
 - 80 
<br/><br/><label>ISBN: </label>9780602575878 
<br/><br/><label>Dewey Class. No.: </label>510  / 2265