@article{10_4153_CJM_1988_005_x,
     author = {Gilman, Jane},
     title = {Inequalities in {Discrete} {Subgroups} of {PSL(2,} {R)}},
     journal = {Canadian journal of mathematics},
     pages = {115--130},
     year = {1988},
     volume = {40},
     number = {1},
     doi = {10.4153/CJM-1988-005-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1988-005-x/}
}