@article{CMH_1991__66_4_140225,
     author = {Vlad Sergiescu and Peter Greenberg},
     title = {An acyclic extension of the braid group.},
     journal = {Commentarii mathematici Helvetici},
     pages = {109--138},
     publisher = {mathdoc},
     volume = {66},
     number = {4},
     year = {1991},
     zbl = {0736.20020},
     url = {http://geodesic.mathdoc.fr/item/CMH_1991__66_4_140225/}
}