What are the dates for the documents with both 'GV' type and 'SF' type expenses?
select t1.document_date from documents as t1 join documents_with_expenses as t2 on t1.document_id = t2.document_id where t2.budget_type_code = 'GV' intersect select t1.document_date from documents as t1 join documents_with_expenses as t2 on t1.document_id = t2.document_id where t2.budget_type_code = 'SF'