@article{DMGT_2012_32_4_a1,
     author = {Dobrynin, Andrey and Mel'nikov, Leonid},
     title = {4-chromatic {Koester} graphs},
     journal = {Discussiones Mathematicae. Graph Theory},
     pages = {617--627},
     publisher = {mathdoc},
     volume = {32},
     number = {4},
     year = {2012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGT_2012_32_4_a1/}
}