Hata, K., Liu, J. and Wang, Z.-Q. (2013) “Note on periodic solutions of relativistic pendulum type systems”, Topological Methods in Nonlinear Analysis, 42(2), pp. 417–425. Available at: https://apcz.umk.pl/TMNA/article/view/TMNA.2013.043 (Accessed: 26 April 2024).