@article{IM_1987__87_143429,
     author = {J.M. Montesinos and H.M. Hilden and M.T. Lozano},
     title = {On universal groups and three-manifolds.},
     journal = {Inventiones mathematicae},
     pages = {441--456},
     publisher = {mathdoc},
     volume = {87},
     year = {1987},
     zbl = {0613.57007},
     url = {http://geodesic.mathdoc.fr/item/IM_1987__87_143429/}
}