Gr. Margaritis, S. “Evaluation of Upper Secondary Schools on Efficiency and Productivity Change in 2016-2019: Empirical Evidence from Schools in the Region in Central Greece”. SPOUDAI Journal of Economics and Business, vol. 71, no. 3-4, Apr. 2021, pp. 101-2, http://spoudai.org/index.php/journal/article/view/100.