The extent of mixing in stellar interiors: the open clusters Collinder 261 and Melotte 66 Arnas Drazdauskas, Gražina Tautvaišienė, Sofia Randich, Angela Bragaglia, Šarūnas Mikolaitis and Rimvydas Janulis A&A, 589 (2016) A50 Published online: 12 April 2016 DOI: 10.1051/0004-6361/201628138