@article{PDMA_2013_6_a33,
     author = {P. P. Bondarenko},
     title = {On the upper bound for the number of additional edges in minimal vertex extensions of colored circles},
     journal = {Prikladnaya Diskretnaya Matematika. Supplement},
     pages = {73--75},
     publisher = {mathdoc},
     number = {6},
     year = {2013},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDMA_2013_6_a33/}
}