On a theorem of Graham

A strengthened form of Gurevichʹs conjecture was proved by R. L. Graham, which says that for any α > 0 and any pair of non-parallel lines L1 and L2, in any partition of the plane into finitely many classes, some class contains the vertices of a triangle which has area α and two sides parallel to the lines Li. In this note, using the main idea of Graham, we present a shorter proof of the result.