Willis, Dave. <br/><br/>
Collins COBUILD student's grammar :  practice material / 
by Dave Willis. 
 - Self study ed. with answer key. 
 - London :  HarperCollins,  1991. 
 - xvii, 263p :  ill. ;  25 cm. 
<br/><br/> "Based on the COBUILD language research project at the University of Birmingham". 
<br/><br/><label>ISBN: </label>0003705633 :  5.50