@article{10_4171_ggd_312,
     author = {Tara C. Davis and Alexander Yu. Olshanskii},
     title = {Relative subgroup growth and subgroup distortion},
     journal = {Groups, geometry, and dynamics},
     pages = {237--273},
     year = {2015},
     volume = {9},
     number = {1},
     doi = {10.4171/ggd/312},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/312/}
}