Technical manual 
Sylvania Radio Tubes                                         
 - 6th ed. 
 - Penna  Sylvania Electric Products  1946 
<br/><br/><label>Subjects--Topical Terms: </label><br/>NASA Thesaurus<br/>Radio Electronics<br/>Tubes
<br/><br/><label>Universal Decimal Class. No.: </label>621.383  / SYL