@article{10_4153_CMB_1978_018_x,
     author = {Berman, David M.},
     title = {Critical {Graphs} for {Acyclic} {Colorings}},
     journal = {Canadian mathematical bulletin},
     pages = {115--116},
     year = {1978},
     volume = {21},
     number = {1},
     doi = {10.4153/CMB-1978-018-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1978-018-x/}
}