@article{DM_2011_23_2_a7,
     author = {M. B. Abrosimov},
     title = {Minimal vertex extensions of directed stars},
     journal = {Diskretnaya Matematika},
     pages = {93--102},
     publisher = {mathdoc},
     volume = {23},
     number = {2},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_2011_23_2_a7/}
}