Richards, Brian J. <br/><br/>
Language development and individual differences :  a study of auxiliary verb learning / 
Brian J. Richards. 
 - Cambridge :  Cambridge University Press,  1990. 
 - 252 p. :  ill. ;  24 cm. 
<br/><br/><label>ISBN: </label>0521362539 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Language acquisition.<br/>Grammar, Comparative and general--Auxiliaries.<br/>Individual differences in children.<br/>English language--Auxiliary verbs.