# 极限环

## 参考来源

• PlanetMath极限环的資料。
• Steven H. Strogatz, "Nonlinear Dynamics and Chaos", Addison Wesley publishing company, 1994.
• M. Vidyasagar, "Nonlinear Systems Analysis, second edition, Prentice Hall, Englewood Cliffs, New Jersey 07632.
• Philip Hartman, "Ordinary Differential Equation", Society for Industrial and Applied Mathematics, 2002.
• Witold Hurewicz, "Lectures on Ordinary Differential Equations", Dover, 2002.
• Solomon Lefschetz, "Differential Equations: Geometric Theory", Dover, 2005.
• Lawrence Perko, "Differential Equations and Dynamical Systems", Springer-Verlag, 2006.