Sodium enrichment of stellar atmospheres - I. Non-variable supergiants and bright giants S. M. Andrievsky, I. A. Egorova, S. A. Korotin and R. Burnage A&A, 389 2 (2002) 519-523 Published online: 27 June 2002 DOI: 10.1051/0004-6361:20020645