@article{PDM_2011_2_a5,
     author = {M. B. Abrosimov},
     title = {Minimal edge extensions of oriented and directed stars},
     journal = {Prikladna\^a diskretna\^a matematika},
     pages = {77--89},
     publisher = {mathdoc},
     number = {2},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDM_2011_2_a5/}
}