@article{JRAM_1995__462_153719,
     author = {Wiebe R. Pestman},
     title = {Minimal bi-invariant {Hilbert} subspaces of distributions on nilpotent {Lie} groups.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {159--168},
     publisher = {mathdoc},
     volume = {462},
     year = {1995},
     zbl = {0820.46035},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1995__462_153719/}
}