Find minimum set of vertices that are reachable from all other vertices

Question

I have a DAG and I wish to find the minimal set of vertices that have a path to all other vertices.

My solution was to simply find all the vertices that their incoming degree is 0. However, if there are two vertices in the DAG that have an indegree of 0 and that point to a common vertex then one of the two vertices is surplus.

Any help appreciated.