Question: what was built in an effort of cooperation between north and south korea
[{'answer': 'Korean Demilitarized Zone', 'provenance': [{'wikipedia_id': '61104', 'title': 'Korean reunification', 'start_paragraph_id': 2, 'start_character': 332, 'end_paragraph_id': 2, 'end_character': 357, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'June 15th North -- South Joint Declaration'}]