  This paper proves the following result: Assume $G$ is a triangle free planar
graph, $X$ is an independent set of $G$. If $L$ is a list assignment of $G$
such that $\mid L(v)\mid = 4$ for each vertex $v \in V(G)-X$ and $\mid L(v)\mid
= 3$ for each vertex $v \in X$, then $G$ is $L$-colourable.
