@article{MAN_1986__276_164218,
     author = {W. Hansen and H. Hueber},
     title = {The {Dirichlet} {Problem} for {Sublaplacians} on {Nilpotent} {Gruops} - {Geometric} {Criteria} {For} {Regularity.}},
     journal = {Mathematische Annalen},
     pages = {537--548},
     publisher = {mathdoc},
     volume = {276},
     year = {1986},
     zbl = {0601.31007},
     url = {http://geodesic.mathdoc.fr/item/MAN_1986__276_164218/}
}