Bounding the number of cycles of O.D.E.S in Rn
Criteria are given under which the boundary of an oriented surface does not consist entirely of trajectories of the C1 differential equation ẋ = f(x) in Rn. The special case of an annulus is further considered, and the criteria are used to deduce sufficient conditions for the differential equation to have at most one cycle. A bound on the number of cycles on surfaces of higher connectivity is given by similar conditions. ©2000 American Mathematical Society.
Farkas, M.; Van Den Driessche, P.; and Zeeman, M. L., "Bounding the number of cycles of O.D.E.S in Rn" (2001). Mathematics Faculty Publications. 77.