1. European Parliament and Council of the European Union, . Directive 2009/28/EC of the european parliament and of the council of 23 april 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing directives 2001/77/EC and 2003/30/EC. Official Journal of the European Union 2009;5:2009.
2. A policy framework for climate and energy in the period from 2020 to 2030. communication from the commissionto the european parliament, the council;Commission,2014
3. Past, current and future of biomass energy research: A bibliometric analysis;Mao;Renewable andSustainable Energy Reviews,2015
4. Biomass resources and their bioenergy potential estimation: A review;Long;Renewable and Sustainable EnergyReviews,2013
5. An overview of feed-in tariffs, premiums and tendersto promote electricity from biogas in the eu-28;Pablo-Romero;Renewable and Sustainable Energy Reviews,2017