Write SQL query to solve given problem: Please list the zip_codes of all the residential areas in Huntingdon county with over 30 employees.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT DISTINCT T1.zip_code FROM zip_data AS T1 INNER JOIN country AS T2 ON T1.zip_code = T2.zip_code WHERE T2.county = 'HUNTINGDON' AND T1.employees > 30