Spatially resolved carbon and oxygen isotopic ratios in NGC 253 using optically thin tracers S. Martín, S. Muller, C. Henkel, D. S. Meier, R. Aladro, K. Sakamoto and P. P. van der Werf A&A, 624 (2019) A125 Published online: 24 April 2019 DOI: 10.1051/0004-6361/201935106