CO isotopolog line fluxes of viscously evolving disks - Cold CO conversion insufficient to explain observed low fluxesL. Trapman, A. D. Bosman, G. Rosotti, M. R. Hogerheijde and E. F. van DishoeckA&A, 649 (2021) A95DOI: https://doi.org/10.1051/0004-6361/202039200