What are the names of the employees who authorised the destruction and the employees who destroyed the corresponding documents?
select t2.employee_name, t3.employee_name from documents_to_be_destroyed as t1 join employees as t2 on t1.destruction_authorised_by_employee_id = t2.employee_id join employees as t3 on t1.destroyed_by_employee_id = t3.employee_id