“…The affine period is widely used in astrophysics. For some interesting results on the affine period, please refer to [12][13][14][15] and the references therein. In [12], using the lower and upper solutions method and topological degree theory, Xu et al claimed that a Newton affine-periodic system admits an affine-periodic; In [13], Liu et al showed that every first-order dissipative-(T, a)affine-periodic system also has a dissipative-(T, a)-affine-periodic solution in [0, ∞) using topological degree theory and the lower and upper solutions method; In [14], Xu et al firstly gave some extremum principles for higher-order affine-periodic systems.…”