@article{10_4171_ggd_440,
     author = {Sergio Estrada and Jos\'e L. Rodr{\'\i}guez},
     title = {Envelopes and covers for groups},
     journal = {Groups, geometry, and dynamics},
     pages = {107--120},
     year = {2018},
     volume = {12},
     number = {1},
     doi = {10.4171/ggd/440},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/440/}
}