@article{MZ_1995__220_1_174816,
     author = {Thomas A. Schmidt and Mark Sheingorn},
     title = {Length spectra of the {Hecke} triangle groups.},
     journal = {Mathematische Zeitschrift},
     pages = {369--398},
     publisher = {mathdoc},
     volume = {220},
     number = {1},
     year = {1995},
     zbl = {0840.11019},
     url = {http://geodesic.mathdoc.fr/item/MZ_1995__220_1_174816/}
}