1. Centre of Environmental Science (CML) and University of Technology (TUD/TB) Fuels and Raw Material Bureau (Bureau B&G) 2001a http://cml.leiden.edu/research/industrialecology/researchprojects/finished/new-dutch-lca-guide.html
2. Centre of Environmental Science (CML) and University of Technology (TUD/TB) 2001b http://cml.leiden.edu/research/industrialecology/researchprojects/finished/new-dutch-lca-guide.html
3. Global Reporting Initiative (GRI) The Sustainability Reporting Guidelines 2006 http://www.globalreporting.org/Home