  A (k,d)-list assignment L of a graph G is a mapping that assigns to each
vertex v a list L(v) of at least k colors and for any adjacent pair xy, the
lists L(x) and L(y) share at most d colors. A graph G is (k,d)-choosable if
there exists an L-coloring of G for every (k,d)-list assignment L. This concept
is also known as choosability with separation.
  It is known that planar graphs are (4,1)-choosable but it is not known if
planar graphs are (3,1)-choosable. We strengthen the result that planar graphs
are (4,1)-choosable by allowing an independent set of vertices to have lists of
size 3 instead of 4.
