Question: what are the two sides of a sand dune
[{'answer': 'stoss ( upflow ) side', 'provenance': [{'wikipedia_id': '7890', 'title': 'Dune', 'start_paragraph_id': 1, 'start_character': 244, 'end_paragraph_id': 1, 'end_character': 264, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': "`` slip face '' in the lee side"}, {'provenance': [{'wikipedia_id': '7890', 'title': 'Dune', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 466, 'bleu_score': 0.9776501033621461, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 128522452723326509}, 'section': 'Section::::Abstract.'}]}]