High-resolution spectroscopic atlas of M subdwarfs. Effective temperature and metallicityA. S. Rajpurohit, C. Reylé, F. Allard, R.-D. Scholz, D. Homeier, M. Schultheis and A. BayoA&A, 564 (2014) A90DOI: https://doi.org/10.1051/0004-6361/201322881