Chodakowska, Ewa, and Joanicjusz Nazarko. “Environmental DEA Method for Assessing Productivity of European Countries”. Technological and Economic Development of Economy 23, no. 4 (June 16, 2017): 589-607. Accessed February 7, 2025. https://mla.vilniustech.lt/index.php/TEDE/article/view/652.