Rezo, Zvonimir, Sanja Steiner, and Tomislav Mihetec. “European Airspace (De)Fragmentation Assessment Model”. Promet - Traffic&Transportation 33, no. 2 (April 6, 2021): 309-318. Accessed May 18, 2021. https://traffic.fpz.hr/index.php/PROMTT/article/view/3645.