Time-varying sodium absorption in the Type Ia supernova 2013gh R. Ferretti, R. Amanullah, A. Goobar, J. Johansson, P. M. Vreeswijk, R. P. Butler, Y. Cao, S. B. Cenko, G. Doran, A. V. Filippenko et al. (11 more) A&A, 592 (2016) A40 Published online: 18 July 2016 DOI: 10.1051/0004-6361/201628351