@article{10_37236_1065,
     author = {J. S. Caughman and J. J. P. Veerman},
     title = {Kernels of directed graph {Laplacians}},
     journal = {The electronic journal of combinatorics},
     year = {2006},
     volume = {13},
     doi = {10.37236/1065},
     zbl = {1097.05026},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/1065/}
}