3 is NP-hard

Arnaud de Mesmay, Yo'av Rieck, Eric Sedgwick, Martin Tancer. 3 is NP-hard. In Artur Czumaj, editor, Proceedings of the Twenty-Ninth Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2018, New Orleans, LA, USA, January 7-10, 2018. pages 1316-1329, SIAM, 2018. [doi]

@inproceedings{MesmayRST18,
  title = {3 is NP-hard},
  author = {Arnaud de Mesmay and Yo'av Rieck and Eric Sedgwick and Martin Tancer},
  year = {2018},
  doi = {10.1137/1.9781611975031.86},
  url = {https://doi.org/10.1137/1.9781611975031.86},
  researchr = {https://researchr.org/publication/MesmayRST18},
  cites = {0},
  citedby = {0},
  pages = {1316-1329},
  booktitle = {Proceedings of the Twenty-Ninth Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2018, New Orleans, LA, USA, January 7-10, 2018},
  editor = {Artur Czumaj},
  publisher = {SIAM},
  isbn = {978-1-61197-503-1},
}