V. B. Silva, J. P. Vieira, and E. D. Leonel, “A New Application of the Normal Form Description to a N-Dimensional Dynamical Systems Attending the Conditions of a Hopf Bifurcation”, JVTSD, vol. 2, no. 3, pp. 249–256, Aug. 2026, doi: 10.5890/JVTSD.2018.09.005.