@Misc{ ledottwar, author = { Le Donne, Enrico and Ottazzi, Alessandro and Warhurst, Ben }, title = { Ultrarigid tangents of sub-Riemannian nilpotent groups }, journal = { }, year = { 2011 }, pages = { }, URL = { http://cvgmt.sns.it/paper/925/ }, note = { cvgmt preprint} }