@article{IM_1993__111_1_144072,
     author = {Masato Tsujii},
     title = {Positive {Lyapunov} exponents in families of one dimensional dynamical systems.},
     journal = {Inventiones mathematicae},
     pages = {113--138},
     publisher = {mathdoc},
     volume = {111},
     number = {1},
     year = {1993},
     zbl = {0787.58029},
     url = {http://geodesic.mathdoc.fr/item/IM_1993__111_1_144072/}
}