Covering the edges of digraphs in mathscr{D}(3,3) and mathscr{D}(4,4) with directed cuts

For nonnegative integers $k$ and $l$, let $\mathscr{D}(k,l)$ denote the family of digraphs in which every vertex has either indegree at most $k$ or outdegree at most $l$. In this paper we prove that the edges of every digraph in $\mathscr{D}(3,3)$ and $\mathscr{D}(4,4)$ can be covered by at most five directed cuts and present an example in $\mathscr{D}(3,3)$ showing that this result is best possible.