1. Task 37 Biogas Country Overview;IEA,2014
2. Annex 1 Directive 2009-28-EC;European C,2012
3. Renewable Energy Directive and the Fuel Quality Directive;European C,2014
4. Census of Agriculture;CSO,2010-2013
5. Fundamental science and engineering of the anaerobic digestion process;Murphy,2013