@article{MOMA_1989__107_3_178424,
     author = {Claudio Nebbia},
     title = {A {Note} on the {Amenable} {Subgroups} of {PSL} (2, {R).}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {241--244},
     publisher = {mathdoc},
     volume = {107},
     number = {3},
     year = {1989},
     zbl = {0679.43008},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1989__107_3_178424/}
}