Tractor ignition :   The magneto. 

 - London-CA :   British farm mechanization,   1949. 
 - página 274 :   ilustraciones blanco y negro 
 - Irregular 
 - Vol. 1, no.8 (Nov.1949) 
 - British farm mechanization. A link between British engineering and world farming ;   no.8 .
 - British farm mechanization. .