Write SQL query to solve given problem: What is the contact URL of Claire McCaskill?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.contact_form FROM current AS T1 INNER JOIN `current-terms` AS T2 ON T1.bioguide_id = T2.bioguide WHERE T1.official_full_name = 'Claire McCaskill' GROUP BY T2.contact_form