  A graph $G$ is $(1,3)$-colorable if its vertices can be partitioned into
subsets $V_1$ and $V_2$ so that every vertex in $G[V_1]$ has degree at most $1$
and every vertex in $G[V_2]$ has degree at most $3$. We prove that every graph
with maximum average degree at most 28/9 is $(1, 3)$-colorable.
