@article{MZ_1996__222_3_174881,
     author = {Lieven Le Bruyn and M. Van den Bergh},
     title = {Central extensions of three dimensional {Artin-Schelter} regular algebras.},
     journal = {Mathematische Zeitschrift},
     pages = {171--212},
     publisher = {mathdoc},
     volume = {222},
     number = {3},
     year = {1996},
     zbl = {0876.17019},
     url = {http://geodesic.mathdoc.fr/item/MZ_1996__222_3_174881/}
}