@article{MZM_1990_47_6_a6,
     author = {V. V. Makeev},
     title = {Extremal covers},
     journal = {Matemati\v{c}eskie zametki},
     pages = {62--66},
     publisher = {mathdoc},
     volume = {47},
     number = {6},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1990_47_6_a6/}
}