A generalization of Hopf's bifurcation problem

The topic presented here is not really a topic of celestial mechanics, because a dissipative system is considered, and dissipative systems do not occur in celestial mechanics at least if drag is not taken into account. Only in the theoretical background of Baumgarte-Stiefel stabilization dissipative systems become important. The only justification is that, in order to establish the result, a tool, namely the method of averaging, is used here which is a good tool for many problems of celestial mechanics too.Proceedings of the Sixth Conference on Mathematical Methods in Celestial Mechanics held at Oberwolfach (West Germany) from 14 to 19 August, 1978.