We discuss in this paper a method of finding skyline or non-dominated points
in a set $P$ of $n_P$ points with respect to a set $S$ of $n_S$ sites. A point
$p_i \in P$ is non-dominated if and only if for each $p_j \in P$, $j \not= i$,
there exists at least one point $s \in S$ that is closer to $p_i$ than $p_j$.
We reduce this problem of determining non-dominated points to the problem of
finding sites that have non-empty cells in an additive Voronoi diagram with a
convex distance function.