Hornby, A.S.. <br/><br/>
Teaching of Structural Words and Sentence patterns /  

 - Fourth Impression 19 /  
 - London W.1 :   The English Language Book Society. 
 - p.402 :  
<br/><br/><label>Dewey Class. No.: </label>P,6:2(T:3)  / K4;2