1. Every planar graph has an acyclic 7-coloring;Albertson;Israel J. Math.,1977
2. On decomposition of graphs into degenerated subgraphs;Borodin;Discretny analys,1976
3. The point arboricity of planar graphs;Chartrand;J. London Math. Soc.,1968
4. Graphs with forbidden subgraphs;Chartrand;J. Combin. Theory,1971
5. Acyclic colorings of planar graphs;Grünbaum;Israel J. Math.,1973