1. Exoo, G., Ismailescu, D.: The Hadwiger-Nelson problem with two forbidden distances. Geombinatorics. XXVIII(1), 51–68 (2018)
2. Exoo, G., Ismailescu, D.: The chromatic number of the plane is at least 5 – a new proof, arXiv:1805.00157, May 2018; and also Discrete Comput. Geom. (2019). https://doi.org/10.1007/s00454-019-00058-1
3. http://cs.indstate.edu/ge/ExooIsmailescuData
4. Exoo, G., Ismailescu, D.: A 6-chromatic two-distance graph in the plane. Geombinatorics. XXIX(3), 97–103 (2020)
5. Exoo, G., Ismailescu, D..: http://cs.indstate.edu/ge/ ExooIsmailescuData/vertices.1.2.graph.txt