Powell, Leonard Sutherland <br/><br/>
A guide to the use of visual aids / 
by L. S. Powell 
 - 3nd ed. 
 - London :  British Association for Commercial and Industrial Education,  1970 
 - 36 p. :  ill. ;  22 cm. 
<br/><br/>Bibliography: p. 39-40 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Visual aids