1. REN- Rede Eléctrica Nacional, S.A. National electricity grid information center. Web: http://www.centrodeinformacao.ren.pt/ (last access 5/02/2011).
2. Eurostat, European Commission. Portugal statistics and indicators section. Web:http://epp.eurostat.ec.europa.eu/portal/page/portal/eurostat/home (last access 10/07/2011).
3. Directive 2003/30/EC
4. Microbial production of hydrogen: an overview;Nandi;Critical Reviews in Microbiology,1998
5. Hybrid plug-in fuel cell vehicles Market penetration Scenarios;Baptista;International Journal of Hydrogen Energy,2010