A very specific request!
The standard covers the requirements for the design, construction, testing, and documentation of low-voltage switchgear and controlgear assemblies, which are used to control and distribute electrical power in low-voltage systems. iec 60439 pdf
IEC 60439 is a standard published by the International Electrotechnical Commission (IEC) that deals with "Low-voltage switchgear and controlgear assemblies". A very specific request
Low-voltage switchgear and controlgear assemblies Publication date: 2015 ( consolidated version) Number of pages: 262 iec 60439 pdf
Here's a detailed overview of the standard: