Question: when did latvia became part of the soviet union
[{'answer': 'August 5 , 1940', 'provenance': [{'wikipedia_id': '17762', 'title': 'History of Latvia', 'start_paragraph_id': 220, 'start_character': 942, 'end_paragraph_id': 220, 'end_character': 957, 'bleu_score': 1.0, 'section': 'Section::::World War II.:Soviet occupation.\n'}]}, {'provenance': [{'wikipedia_id': '17762', 'title': 'History of Latvia', 'start_paragraph_id': 220, 'start_character': 0, 'end_paragraph_id': 220, 'end_character': 1063, 'bleu_score': 0.957378749190096, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13816772239757106607}, 'section': 'Section::::World War II.:Soviet occupation.\n'}]}]