1. G. Aloupis, E.D. Demaine, A. Guo, G. Viglietta, Classic nintendo games are (computationally) hard, in: Proc. Fun with Algorithms, FUN2014, in: LNCS, vol. 8496, 2014, pp. 40–51.
2. Hashiwokakero is NP-complete;Andersson;Inform. Process. Lett.,2009
3. Every planar map is four colorable part i. Discharging;Appel;Illinois J. Math.,1977
4. Solution of the four color map problem;Appel;Sci. Am.,1977
5. Every planar map is four colorable part ii. Reducibility;Appel;Illinois J. Math.,1977