DIN EN 60061-1:2017
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 A51:2014 + A52:2015 + A53:2015, modified); German version EN 60061-1:1993 + A1:1