I. Penkov, D. Aleksandrov. Analysis and study of the influence of the geometrical parameters of mini unmanned quad-rotor helicopters to optimise energy saving . Int. J. Automot. Mech. Eng. [Internet]. 2022 Dec. 9 [cited 2024 May 19];14(4):4730-46. Available from: https://journal.ump.edu.my/ijame/article/view/8011