Question: when did trolley buses stop running in belfast
[{'answer': '12 May 1968', 'provenance': [{'wikipedia_id': '31220073', 'title': 'Trolleybuses in Belfast', 'start_paragraph_id': 7, 'start_character': 567, 'end_paragraph_id': 7, 'end_character': 578, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '31220073', 'title': 'Trolleybuses in Belfast', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 190, 'bleu_score': 0.8022998220952821, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2024326268949000996}, 'section': 'Section::::Abstract.'}]}]