@article{10_37236_120,
     author = {Clara E. Brasseur and Ryan E. Grady and Stratos Prassidis},
     title = {Coverings, {Laplacians,} and heat kernels of directed graphs},
     journal = {The electronic journal of combinatorics},
     year = {2009},
     volume = {16},
     number = {1},
     doi = {10.37236/120},
     zbl = {1181.05059},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/120/}
}