1. EPA. Energy policy act; 2009, http://www.seco.cpa.state.tx.us/energy-sources/biomass/epact2005.php.
2. Zolin MB. Biomass energy: new opportunity for agriculture and marginal areas, Working Papers; 2008, dse.unive.it.
3. Political economic and environmental impacts of biofuel: a review;Demirbas;Applied Energy,2009
4. Redman G. Assessment of on-farm AD in the UK, The Andersons Centre, National Non-Food Crops Centre, 09.06.08 [retrieved 11.05.09].
5. UNEP, United Nation Energy Program; 2009, http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=512&ArticleID=5616&l=en.