@article{10_4171_ggd_111,
     author = {Walter D. Neumann},
     title = {On {Leighton{\textquoteright}s} graph covering theorem},
     journal = {Groups, geometry, and dynamics},
     pages = {863--872},
     year = {2010},
     volume = {4},
     number = {4},
     doi = {10.4171/ggd/111},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/111/}
}