Powell, Leonard Sutherland. <br/><br/>
A guide to the use of visual aids/  English. 
L. S. Powell. 
 - London:  British Association for Commercial and Industrial Education,  1961. 
 - 36p.:  ill.;  22 cm. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Visual aids.
<br/><br/><label>Dewey Class. No.: </label>658.386:371.33  / POW