@article{ZNSL_2012_406_a5,
     author = {G. V. Nenashev},
     title = {On existence of noncritical vertices in digraphs},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {107--116},
     publisher = {mathdoc},
     volume = {406},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2012_406_a5/}
}