DIN 83402-1
DIN 83402-1 Manhole covers 600 × 400 for pressures up to 1.1 bar or 3 bar - Part 1: Assembly, installation
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 03/01/2006
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 03/01/2006