@article{PDM_2015_4_a7,
     author = {A. Yu. Zubov},
     title = {About some classes of extremal oriented graphs},
     journal = {Prikladna\^a diskretna\^a matematika},
     pages = {83--90},
     publisher = {mathdoc},
     number = {4},
     year = {2015},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDM_2015_4_a7/}
}