“…It is well known that there exists at least one entire trajectory through each point a ∈ A that is contained in A, i.e., there exists a mapping χ : R → X such that χ(t + s) = ϕ(s, χ(t)) for all t ∈ R and s ∈ R + , with χ(0) = a and χ(t) ∈ A for all t ∈ R. Positively invariant sets are often encountered from absorbing sets, which is a first step to prove the existence of an attractor. Negatively invariant sets are not discussed directly so often in the literature, e.g., [13], but are present in many unstable situations such as following the loss of stability in a bifurcation or on an unstable manifold about an equilibrium point as well as in discretization and persistency problems, e.g., [2,3,4,6,12,17,18,19].…”