Dummer, G.W.A <br/><br/>
Variable resistors and potentiometers 

 - London  Sir Isaac Pitman & sons Ltd.  1963 
 - xi+228p 
 -  Radio and Electronic components Vol. <2=two> .
<br/><br/><label>Universal Decimal Class. No.: </label>621.316.8  / : 621.317.727.2 DUM.63