Let F be a continuous map of a closed ball in ${\mathbb R}^m$ to ${\mathbb R}^n$ where $m\ge n$. Suppose that F is open i.e. images of all open sets are open. Is it true that for any point of the interior of the image of F, the image of any sufficiently $C^0$ close maps covers this point?
I believe, this must be something about Topologic Index Theory.