@article{DM_2012_24_2_a5,
     author = {D. S. Malyshev},
     title = {On intersection and symmetric difference of families of boundary classes in the problems on colouring and on the chromatic number},
     journal = {Diskretnaya Matematika},
     pages = {75--78},
     publisher = {mathdoc},
     volume = {24},
     number = {2},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_2012_24_2_a5/}
}