@article{10_2307_121018,
     author = {Zheng-Xu He},
     title = {Rigidity of infinite disk patterns},
     journal = {Annals of mathematics},
     year = {1999},
     volume = {149},
     number = {1},
     doi = {10.2307/121018},
     zbl = {0922.30020},
     url = {http://geodesic.mathdoc.fr/articles/10.2307/121018/}
}