DIN EN 60061-1/E21:2007
Lamp caps and holders together with gauges for the control of interchangeability and safety- Part 1: Lamp caps (IEC 60061-1-1969+supplements A:1970 to V:1997+A21:1998 to A38:2006, modified); German version EN 60061-1:1993+A1:1995 to A7:1997+A21:1988 to