suppose a submodule V of Q as a Z-module is generated by <$q_1$, $q_2$>, let $q_1$ = $\frac{a_1}{b_1}$, $q_2$ = $\frac{a_2}{b_2}$, so V is generated by <$\frac{gcd(a_1b_2, a_2b_1)}{b_1b_2}$>.
When V is generated by <$q_1$, $q_2$, ..., $q_n$>, the processing is similar to the one described above.
Is there anything wrong?
