Evaluating the state of the art of photovoltaic performance modelling in EuropeWilliams, S.; Betts, T.; Krustok, JüriProceedings of the 20th European Photovoltaic Solar Energy Conference2006 / p. 1937-1941http://staff.ttu.ee/~juri.krustok/PDF-s/williams%20et%20al.pdf