@article{IM_1988__93_2_143611,
     author = {T. Nowicki and S. van Strien},
     title = {Absolutely continuous invariant measures for {C2} unimodal maps satisfying the {Collet-Eckmann} conditions.},
     journal = {Inventiones mathematicae},
     pages = {619--636},
     publisher = {mathdoc},
     volume = {93},
     number = {2},
     year = {1988},
     zbl = {0659.58034},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__93_2_143611/}
}