http://ec.europa.eu/enterprise/sectors/pressure-and-gas/documents/gad/  for information about the 2009/142/EC Gas Appliance Directive
http://ec.europa.eu/enterprise/sectors/pressure-and-gas/documents/gad/guidances/index_en.htm for information about Guidance sheets related to the 2009/142/EC Gas Appliance Directive

http://iate.europa.eu/iatediff/SearchByQueryLoad.do;jsessionid=9ea7991930d798c8b51fcd294acaa927e34fb61e0107.e38KbN4MchyMb40SbxyRaxyTbNz0?method=load for translations
http://www.aardgas.be for more information about the Belgian Gas Association