CMO 2007 Problem 2

You are given a pair of triangles for which two sides of one triangle are equal in length to two sides of the second triangle, and the triangles are similar, but not necessarily congruent. Prove that the ratio of the sides that correspond under the similarity is a number between $\frac {1}{2}(\sqrt {5} - 1)$ and $\frac {1}{2}(\sqrt {5} + 1)$ .