Question: when was the euro introduced as legal currency in the world market
[{'answer': '1 January 1999', 'provenance': [{'wikipedia_id': '9472', 'title': 'Euro', 'start_paragraph_id': 5, 'start_character': 150, 'end_paragraph_id': 5, 'end_character': 164, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '9472', 'title': 'Euro', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 865, 'bleu_score': 0.685529419483447, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2707485366195050699}, 'section': 'Section::::Abstract.'}]}]