Atomic Diffusion and Mixing in Old Stars. I. Very Large Telescope FLAMES‐UVES Observations of Stars in NGC 6397
                         
                    
                    
                    
                        - Authors: A. J. Korn, F. Grundahl, O. Richard, L. Mashonkina, P. S. Barklem, R. Collet, B. Gustafsson, and N. Piskunov
                        Korn  et al. 
                        2007 The Astrophysical Journal 671
                         402.