The shifting strategy is described and the “shifting lemma” is proved in Section
2. We then proceed in Section 3 with its application to problems of covering with
balls and derive a polynomial approximation scheme for this case. We further
explain the behavior of such schemes for problems of covering with arbitrarily
shaped objects in higher dimensional spaces. In Section 4 we describe the application
to packing problems with convex objects, and we summarize our results in
Section 5.