Maksymenko, S.I.
(Український математичний журнал, 2010)
Let F:M×R→M be a continuous flow on a manifold M, let V ⊂ M be an open subset, and let ξ:V→R be a continuous function. We say that ξ is a period function if F(x, ξ(x)) = x for all x ∈ V. Recently, for any open connected ...