Chemical abundance analysis of the old, rich open cluster Trumpler 20 Giovanni Carraro, Sandro Villanova, Lorenzo Monaco, Giacomo Beccari, Javier A. Ahumada and Henri M. J. Boffin A&A, 562 (2014) A39 Published online: 06 February 2014 DOI: 10.1051/0004-6361/201322783