MNRAS paper on ArXiv by K. Altwegg, H. Balsiger, M. Combi, J. De Keyser, M. N. Drozdovskaya, S. A. Fuselier, T. I. Gombosi, N. Hänni, M. Rubin, M. Schuhmann, I. Schroeder, S. Wampfler

https://arxiv.org/abs/2012.05788

Considers isotopic enrichment ratios in various volatile species in 67P, including CO, CO2, water, methanol and formaldehyde, and their underlying chemical origin.