Question: when were tobacco ads banned in the us
[{'answer': 'the 1970s', 'provenance': [{'wikipedia_id': '2199688', 'title': 'Nicotine marketing', 'start_paragraph_id': 49, 'start_character': 468, 'end_paragraph_id': 49, 'end_character': 477, 'bleu_score': 1.0, 'section': 'Section::::Methods.:Non-addictiveness and healthiness.:"Modified risk" products.:Ventilated ("light") cigarettes.\n'}]}]