@Article{ mag04, author = { Magnani, Valentino }, title = { Unrectifiability and rigidity in stratified groups }, journal = { Arch. Math. }, year = { 2004 }, volume = { 83 }, number = { 6 }, pages = { 568-576 }, URL = { http://cvgmt.sns.it/paper/420/ }, note = { cvgmt preprint} }