Question: who sings lead on for what it's worth
[{'answer': 'Buffalo Springfield', 'provenance': [{'wikipedia_id': '1215271', 'title': "For What It's Worth", 'start_paragraph_id': 1, 'start_character': 154, 'end_paragraph_id': 1, 'end_character': 173, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]