Return to Question

Let $F$ be a totally real number field, $R$ is a quaternion algebra over $F$ ramified in at least one infinite place of $F$. Let $\mathcal{O}\subset R$ be an order. By assumption on $R$ its group of units $\mathcal{O}^{\times}$ is a finite(possibly non-commutative) group.

How one can compute it?

Let $F$ be a totally real number field, $R$ is a quaternion algebra over $F$ ramified in all infinite places of $F$. Let $\mathcal{O}\subset R$ be an order. By assumption on $R$ its group of units $\mathcal{O}^{\times}/\mathcal{O}^{\times}_F$ is a finite(possibly non-commutative) group.

How one can compute it?