@article{Boeklen2009,
  author    = {Otto B{\"o}klen},
  title     = {Ueber geod{\"a}tische Linien},
  journal   = {Zeitschrift f{\"u}r Mathematik und Physik},
  volume    = {26},
  pages     = {264 -- 269},
  year      = {2009},
}