@article{IM_1987__89_143481,
     author = {B. Rodin},
     title = {Schwarz's lemma for circle packings.},
     journal = {Inventiones mathematicae},
     pages = {271--290},
     year = {1987},
     volume = {89},
     zbl = {0634.30009},
     url = {http://geodesic.mathdoc.fr/item/IM_1987__89_143481/}
}