@article{10_37236_10005,
     author = {Denis  Krotov},
     title = {Perfect colorings of the infinite square grid: coverings and twin colors},
     journal = {The electronic journal of combinatorics},
     year = {2023},
     volume = {30},
     number = {2},
     doi = {10.37236/10005},
     zbl = {1511.05079},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/10005/}
}