IEC 60999-1 Ed. 2.0 b:1999
Connecting devices - Electrical copper conductors - Safety requirements for screw-type and screwless-type clamping units - Part 1: General requirements and particular requirements for clamping units for conductors from 0,2 mm2 up to 35 mm2 (included)standard by International Electrotechnical Commission, 11/30/1999