Husen Torsten. <br/><br/>
The International Encyclopaedia of Education-Vol.8 

 - 2nd 
 - England  Pergamon  1994 
 - ix,4337-49 
<br/><br/><label>ISBN: </label>0-08-041046-4 
<br/><br/><label>Dewey Class. No.: </label>370.3