@article{10_4171_ggd_615,
     author = {Yulan Qing and Kasra Rafi},
     title = {Convexity of balls in outer space},
     journal = {Groups, geometry, and dynamics},
     pages = {893--934},
     year = {2021},
     volume = {15},
     number = {3},
     doi = {10.4171/ggd/615},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/615/}
}