For grants with both documents described as 'Regular' and documents described as 'Initial Application', list its start date.
select t1.grant_start_date from grants as t1 join documents as t2 on t1.grant_id = t2.grant_id join document_types as t3 on t2.document_type_code = t3.document_type_code where t3.document_description = 'Regular' intersect select t1.grant_start_date from grants as t1 join documents as t2 on t1.grant_id = t2.grant_id join document_types as t3 on t2.document_type_code = t3.document_type_code where t3.document_description = 'Initial Application'