V. Viktorovich Efimov, K. Olegovich Chernigin, N. Ivanovich Nikolaykin, V. Vadimovich Vorob’ev, and M. Semenovich Kublanov, “Mathematical Modeling of Helicopter Dynamics with an External Sling Load”, IJET, vol. 7, no. 4.38, pp. 1112–1114, Dec. 2018, doi: 10.14419/ijet.v7i4.38.27652.