1. International Energy Agency (IEA). Key World Energy Trends, except from: Renewables Information.
2. Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions;EC,2007
3. Presidency Conclusions to the European Council of 29/30 October 2009;European Council,2009
4. State of the Art Electricity Storage Systems. Indispensable Elements of the Energy Revolution;Auer,2012
5. Speicherung elektrischer Energie – technologie zur Netzintegration erneuerbarer Energien;Doetsch;UWF Umw. Wirtsch. Forum,2009