[1] GALLAI T.: Kritische Graphen I. Publ. Math. Inst. Hung. Acad. Sc., 8, 1963, 165-192. MR 0188099 | Zbl 0121.18401

[2] HARARY F.: Graph Theory. Addison-Wesley, Reading, Mass. 1969. MR 0256911 | Zbl 0196.27202

[3] CHARTRAND G., KRONK H. V., WALL C. E.: The point-arboricity of a graph. Israel J. Math., 6, 1968, 169-175. MR 0236049 | Zbl 0164.54201

[4] CHARTRAND G., KRONK H. V.: The point-arboricity of planar graphs. J. London Math. Soc., 44, 1969, 612-616. MR 0239996 | Zbl 0175.50505

[5] KRONK H. V., MITCHEM J.: Critical point-arboritic graphs. J. London Math. Soc., (2) 9, 1975, 459-466. MR 0360334 | Zbl 0298.05132