Abundances in a sample of turnoff and subgiant stars in NGC 6121 (M 4)M. Spite, F. Spite, A. J. Gallagher, L. Monaco, P. Bonifacio, E. Caffau and S. VillanovaA&A, 594 (2016) A79DOI: https://doi.org/10.1051/0004-6361/201628759