Ammonia-methane ratios from H-band near-infrared spectra of late-T and Y dwarfs E. L. Martín, J.-Y. Zhang, P. Esparza, F. Gracia, J. L. Rasilla, T. Masseron and A. J. Burgasser A&A, 655 (2021) L3 Published online: 25 November 2021 DOI: 10.1051/0004-6361/202142470