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}, }