1. Hirsch, M.W., Smale, S., Devaney, R.L.: Differential equations, dyanmical systems, and an introduction to chaos (in Chinese), 3rd edition, J C Fu. H Y L translate. Harbin Institute of Technology Press, Heilongjiang (2020)
2. McLachlan, R.I., Quispel, G.R.W., Robidoux, N.: Geometric integration using discrete gradients. Philos. Trans. R. Soc. Lond. A 357, 1021–1045 (1999)
3. Mei, F.X., Wu, H.B.: Gradient Representations of Constrained Mechancial Systems (I, II) (in Chinese). Science Press, Beijing (2015)
4. Mei, F.X., Wu, H.B.: The generalized Birkhoff system and a type of combined gradient system. Acta Phys. Sin. 64, 184501–184505 (2015)
5. Chen, X.W., Mei, F.X.: Constrained mechanical systems and gradient systems with strong Lyapunov functions. Mech. Res. Commun. 76, 91–95 (2016). https://doi.org/10.1016/j.mechrescom.2016.07.003