Buică, A., Giné, J. and Llibre, J. (2016) “Periodic solutions for nonlinear differential systems: the second order bifurcation function”, Topological Methods in Nonlinear Analysis, 43(2), pp. 403–419. Available at: https://apcz.umk.pl/TMNA/article/view/TMNA.2014.024 (Accessed: 24 April 2024).