1. Every planar map is four colorable. Part 1: Discharging;Appel;Illinois J. Math.,1977
2. Every planar map is four colorable. Part 2: Reducibility;Appel;Illinois J. Math.,1977
3. A proof of Grnbaum’s conjecture on the acyclic 5-colorability of planar graphs;Borodin;Dokl. Akad. Nauk SSSR,1976
4. On the partition of a planar graph of girth 5 into an empty and an acyclic subgraph;Borodin;Diskretnyi Analiz I Issledovanie Operatsii,2001
5. The point-arboricity of planar graphs;Chartrand;J. Lond. Math. Soc.,1969