Question: how long were the vikings present in north america
[{'answer': 'almost 500 years', 'provenance': [{'wikipedia_id': '295764', 'title': 'Norse colonization of North America', 'start_paragraph_id': 2, 'start_character': 75, 'end_paragraph_id': 2, 'end_character': 91, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '295764', 'title': 'Norse colonization of North America', 'start_paragraph_id': 2, 'start_character': 54, 'end_paragraph_id': 2, 'end_character': 379, 'bleu_score': 0.64369720356528, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18360260436677242734}, 'section': 'Section::::Abstract.'}]}]