@article{10_4171_dm_247,
     author = {Alex Kumjian and David Pask and Aidan Sims},
     title = {$C^*$-algebras associated to coverings of $k$-graphs},
     journal = {Documenta mathematica},
     pages = {161--205},
     year = {2008},
     volume = {13},
     doi = {10.4171/dm/247},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/247/}
}