https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/World_Map_of_Mains_Voltages_and_Frequencies%2C_Detailed.svg/1024px-World_Map_of_Mains_Voltages_and_Frequencies%2C_Detailed.svg.png
Mains electricity by country
https://en.wikipedia.org/wiki/Mains_electricity_by_country
