1. D. Bienstock and N. Dean, Bounds for rectilinear crossing numbers, J. Graph Theory 17 (1993), 333–348.
2. J. Blažek and M. Koman, A minimal problem concerning complete plane graphs, In: Theory of Graphs and Its Applications (ed. M. Fiedler), Czechoslovak Academy of Sciences (1964), 113–117.
3. Alex Brodsky, Stephane Durocher, and Ellen Gethner, The rectilinear crossing number of K 10 is 62, Electron. J. Combin. 8, No. 1 (2001), Research Paper 23, 1–30.
4. H. E. Dudeney, Perplexities, Strand Magazine 46, No. 271 (July 1913), 110; solution in Strand Magazine 46, No. 272 (August 1913), 221.
5. H. E. Dudeney, Amusements in Mathematics, Thomas Nelson and Sons (1917), Problem 251 and solution, 73, 200.