1. Topologie;Alexandroff,1935
2. Theory of Ordinary Differential Equations;Coddington,1955
3. A general bifurcation theorem;Cronin,1977
4. Abzweigung einer periodischen Lösung von einer stationaren Lösung eines Differential-systems;Hopf;Ber. Math.-Phys. Sachsische Akad. Wissenschaften, Leipzig,1942
5. An applicable Hopf bifurcation formula and instability of small periodic solutions of the Field-Noyes model;Hsü;J. Math. Anal. Appl.,1976