1. P. S. Alexandroff-H. Hopf,Topologie, Springer (Berlin, 1935).
2. A. Frank,Combinatorial algorithms, algorithmic proofs. Doctoral dissertation (Budapest, 1975) (in Hungarian).
3. E. Győry, On division of graphs to connected subgraphs; to appear in theProceedings of the Fifth Hungarian Combinatorial Colloquium (Budapest, 1977).