Question: who wrote an essay on the principle of population
[{'answer': 'Thomas Robert Malthus', 'provenance': [{'wikipedia_id': '3563054', 'title': 'An Essay on the Principle of Population', 'start_paragraph_id': 1, 'start_character': 128, 'end_paragraph_id': 1, 'end_character': 149, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3563054', 'title': 'An Essay on the Principle of Population', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 380, 'bleu_score': 0.9657992495762461, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12435240635617417140}, 'section': 'Section::::Abstract.'}]}]