In right triangles $△XYZ$ and $△PQR$, $\angle Y=90^{\circ }$ and $\angle X=30^{\circ }$, $\angle Q=90^{\circ }$ and $\angle P=30^{\circ }$. Which additional piece of information is sufficient to determine whether triangle $△XYZ$ is congruent to triangle $△PQR$?