1. Biomass Program, USA (2006). See also .
2. R. Walt, Modular Biopower Systems for the 21st Century, Community Power Corporation, USA (2007). See also: http://www.gocp.com.
3. World Energy Council, Energy & Climate Change. See also, < http://www.worldenergy.org/wec-geis/publications/reports/ecc/ecc.asp>.
4. ADENE – Portuguese Energy Agency, (2009). See also < hpp://ww.adene.pt>.
5. Energy, energy efficiency, and built environment;Wilkinson;Lancet,2007