Tracing gas accretion in the Galactic center using isotopic ratios D. Riquelme, M. A. Amo-Baladrón, J. Martín-Pintado, R. Mauersberger, S. Martín and L. Bronfman A&A, 523 (2010) A51 Published online: 16 November 2010 DOI: 10.1051/0004-6361/201015008