1. Abraham, R., and Robbin, J. (1967).Transversal Mappings and Flows, W. A. Benjamin, New York.
2. Chen, X.-Y., and Poláčik, P. (1993). Gradient-like structure and morse decompositions for time-periodic one-dimensional parabolic equations (preprint).
3. Conley, C. (1978).Isolated Invariant Sets and the Morse Index, AMS, Providence.
4. Contemporary Mathematics;J. Franks,1988
5. Hurley, M. (1982). Attractors: Persistence, and density of their basins.Trans. AMS 269, 247–271.