@article{UMJ_2020_6_2_a5,
     author = {Konstantin S. Efimov and Alexander A. Makhnev},
     title = {Distance-regular graph with intersection array $\{27, 20, 7; 1, 4, 21\}$ does not exist},
     journal = {Ural mathematical journal},
     pages = {63--67},
     publisher = {mathdoc},
     volume = {6},
     number = {2},
     year = {2020},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UMJ_2020_6_2_a5/}
}