Borodin, O. V. Solution of Ringel’s problems concerning the vertex-faced coloring of planar graphs and the coloring of 1-planar graphs. (Russian) Zbl 0565.05027 Metody Diskretn. Anal. 41, 12-26 (1984). The author proves that the coupled colouring number of any plane graph does not exceed 6, settling thereby a conjecture of G. Ringel [Ein Sechsfarbenproblem auf der Kugel, Abh. Math. Semin. Univ. Hamb., 29, 107- 117 (1965; Zbl 0132.207)]. For a related result on graphs embedded on the projective plane, see H. Schumacher [Abh. Math. Semin. Univ. Hamb. 54, 5-14 (1984; Zbl 0557.05037)]. Reviewer: J.Širáň Cited in 4 ReviewsCited in 67 Documents MSC: 05C15 Coloring of graphs and hypergraphs 05C10 Planar graphs; geometric and topological aspects of graph theory Keywords:coupled colouring number; plane graph PDF BibTeX XML Cite \textit{O. V. Borodin}, Metody Diskretn. Anal. 41, 12--26 (1984; Zbl 0565.05027)