Contribution of HI-bearing ultra-diffuse galaxies to the cosmic number density of galaxies M. G. Jones, E. Papastergis, V. Pandya, L. Leisman, A. J. Romanowsky, L. Y. A. Yung, R. S. Somerville and E. A. K. Adams A&A, 614 (2018) A21 Published online: 07 June 2018 DOI: 10.1051/0004-6361/201732409