Gerlach, Vernon S. <br/><br/>
Teaching and media :  a systematic approach / 
Vernon S.Gerlach, Donald P.Ely, Rob Melnick. 
 - 2nd ed. 
 - Englewood Cliffs, N.J. :  Prentice-Hall ,  1980. 
 - 420p. ,  24cm. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Audio--Visual education.<br/>Teaching--Aids and devices.