Krizanic, F., Z. J. Oplotnik, V. Kolsek, and A. Kavkler. “Production Factors Use in the European Electricity Producing Companies During the Last Financial Crisis”. International Journal of Energy Economics and Policy, vol. 5, no. 3, July 2015, pp. 725-30, https://econjournals.com/index.php/ijeep/article/view/1246.