Drupka, Grzegorz, Andrzej Majka, Tomasz Rogalski, and Leszek Trela. 2018. “An Airspace Model Aplicable for Automatic Flight Route Planning Inside Free Route Airspace”. Advances in Mechanical and Materials Engineering 35 (298 (1), 5-18. https://doi.org/10.7862/rm.2018.01.