ner_tags: O O O O O O O O O O O O B-Person I-Person O O O O B-Person O O O O B-Organization B-Person O O O O O B-Organization I-Organization I-Organization I-Organization I-Organization I-Organization O O O B-Grant
tokens: We thank the referee for the interesting comments. We are grateful to Emmanuel Bertin for many enlightening discussions. F.D. acknowledges long-term support from CNES. I.M. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through the grant AYA2013-42227P.