“…(4.41b), another center manifold reduction scheme (called by him "the reduction scheme of the second category"), which starts with an infinite, or finite, system of ordinary differential equations (in the cases where original equations are partial-differential, this system can be derived by means of a Galerkin projection or/and a normal-mode expansion). Such reduction scheme was used, in particular, in the above-mentioned papers by Guckenheimer and Knobloch, Cheng and Chang, and Chen et al The main objecjtive of Fujimura (1997) was to prove the equivalence of Landau's equations, as given by this reduction scheme, to those derived by the method of multiple scales. To reduce the Navier-Stokes equations to a system of ordimary differential equations, a double expansion of flow fields in Fourier series and in eigenfunctions of the linear stability theory was used.…”