@article{MOMA_1997__123_1_178760,
     author = {Mark Pollicott and Richard Sharp},
     title = {The {Circle} {Problem} on {Surfaces} of {Variable} {Negative} {Curvature.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {61--70},
     publisher = {mathdoc},
     volume = {123},
     number = {1},
     year = {1997},
     zbl = {0876.58040},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1997__123_1_178760/}
}