Training, memory and universal scaling in amorphous frictional granular matter M. M. Bandi, H. G. E. Hentschel, I. Procaccia, S. Roy and J. Zylberg EPL, 122 3 (2018) 38003 Published online: 22 June 2018 DOI: 10.1209/0295-5075/122/38003