1. Renewable energy in the world.
https://en.wikipedia.org/wiki/Renewable_energy
. Accessed Mar 2017
2. Solar & thermal energy - Stecasolar site.
www.stecasolar.ro/energie-solara/Energie-solara-termica-:-Istoric–a714.html
. Accessed Mar 2017
3. An Assessment of Solar Energy Conversion Technologies and Research Opportunities, vol. GCEP Energy Assessment Analysis Summer 2006, issued by Global Climate & Energy Project. Stanford University.
http://gcep.stanford.edu
. Accessed May 2017
4. Janssen, R.: Towards Energy Efficient Buildings in Europe. The European Alliance of Companies for Energy Efficiency in Buildings, London (2004)
5. Renewable energy technologies: Cost analyses of solar photovoltaics. Power Sector - Solar Photovoltaics, vol. 1(4/5). IRENA International Renewable Energy Agency, Abu-Dhabi (2012)