Published online by Cambridge University Press: 20 November 2018
Let M n and Np be separable manifolds of dimensions n and p, respectively, with n ≧ p, and without boundary unless otherwise indicated. A mapƒ: M → N is proper if, for each compact set K ⊂ N, f –l(K) is compact. It is topologically equivalent to g: X → Y if there exist homeomorphisms α of M onto X and β of N onto Y such that βƒα–1 = g. At x ∈ M, ƒ is locally topologically equivalent to g if, for every neighbourhood W ⊂ M of x, there exist neighbourhoods U ⊂ W of x and V of ƒ(x) such that ƒ | U: U → V is topologically equivalent to g.