@article{IM_1987__88_143470,
     author = {G. Levitt},
     title = {1-formes ferm\'ees singuli\`eres et groupe fondamental.},
     journal = {Inventiones mathematicae},
     pages = {635--667},
     publisher = {mathdoc},
     volume = {88},
     year = {1987},
     zbl = {0594.57014},
     url = {http://geodesic.mathdoc.fr/item/IM_1987__88_143470/}
}