1. R. Matsyuk, “On the variationality of geodesic circles in Euclidean spaces E2 and E3,” in: Nonclassical Problems of the Theory of Differential Equations: Collection of Scientific Works Dedicated to the 80th Birthday of B. I. Ptashnyk [in Ukrainian], Pidstryhach Institute for Applied Problems in Mechanics and Mathematics, Ukrainian National Academy of Sciences, Lviv (2017), pp. 173–183.
2. R. Ya. Matsyuk, “Variational generalization of the free relativistic top,” Fiz. Zbirnyk NTSh, 6, 206–214 (2006).
3. V. Ya. Skorobohat’ko, “Equations of geodesic lines in mechanics with higher derivatives,” Dopov. Akad. Nauk Ukr. RSR, Ser. A, No. 10, 897–899 (1970).
4. R. Matsyuk, “Second order variational problem and 2-dimensional concircular geometry,” Travaux Mathématiques, XVIII, 125–137 (2008).
5. R. Ya. Matsyuk, “Inverse variational problem and symmetry in action: the relativistic third order dynamics,” in: D. V. Zenkov (editor), The Inverse Problem of the Calculus of Variations. Local and Global Theory, Ser. Atlantis Studies in Variational Geometry, Vol. 2, Atlantis Press (2015), pp. 75–102.