1. Sunshine Energyhttp://www.inforse.org/europe/fae/OEZ/slnko/slnko.html#TOP
2. Average Sunshine a Year at Cities in Europe—Current Resultshttps://www.currentresults.com/Weather/Europe/Cities/sunshine-annual-average.php
3. Possibilities of Using Solar Energyhttp://www.aee-now.at/cms/fileadmin/downloads/projekte/Homepageuploads/Infosolar_ECB_Moznosti_vyuzivania_slnecnej_energie.pdf
4. Fotovoltaika: Energies from the Sun;Urtinger,2007
5. Sapa Solar Buildinghttp://www.sapabuildingsystems.com/globalassets/sapa-building-systems-ab/pictures/brochures/solar_bipv_low.pdf?ts=636316455108630000