@Article{ mag01, author = { Magnani, Valentino }, title = { A Blow-up Theorem for regular hypersurfaces on nilpotent groups }, journal = { Manuscripta Math. }, year = { 2003 }, volume = { 110 }, number = { 1 }, pages = { 55-76 }, URL = { http://cvgmt.sns.it/paper/851/ }, note = { cvgmt preprint} }