@misc{RCM_2010_44_1_a0,
     title = {Commensurator {Subgroups} of {Surface} {Groups}},
     journal = {Revista colombiana de matematicas},
     pages = {1--13},
     year = {2010},
     volume = {44},
     number = {1},
     url = {http://geodesic.mathdoc.fr/item/RCM_2010_44_1_a0/}
}