Shallow extra mixing in solar twins inferred from Be abundances M. Tucci Maia, J. Meléndez, M. Castro, M. Asplund, I. Ramírez, T. R. Monroe, J. D. do Nascimento Jr. and D. Yong A&A, 576 (2015) L10 Published online: 02 April 2015 DOI: 10.1051/0004-6361/201425357