Addition and subtraction :  a cognitive perspective / 
eidted by Thomas P. Carpenter, James M. Moser, Thomas A. Romberg 
 - Hillsdale, N. J. :  Lawrence Erlbaum Associates,  1982 
 - 245 p. ;  27 cm. 
<br/><br/><label>ISBN: </label>0898591716 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Addition<br/>Subtraction<br/>Mathematical ability--Testing