O´Connell, Susan. <br/><br/>
Mastering the basic math facts in addition and subtraction  strategies, activities & interventions to move students beyond memorization 
Susan O´Connell 
 - ed. 
 -  Heinemann  2011 
 - 156 p. + 1 cd 
<br/><br/><label>ISBN: </label>9780325029634