@article{10_4153_CMB_1978_069_9,
     author = {Coxeter, H. S. M.},
     title = {Parallel {Lines}},
     journal = {Canadian mathematical bulletin},
     pages = {385--397},
     year = {1978},
     volume = {21},
     number = {4},
     doi = {10.4153/CMB-1978-069-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1978-069-9/}
}