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Covering of graphs by complete bipartite subgraphs; complexity of 0-1 matrices. (English) Zbl 0559.05050
The author proves that the edge set of an arbitrary graph G on n vertices can be covered by at most $$n-[\log_ 2n]+1$$ complete bipartite subgraphs of G. This result improves the upper bound of J. C. Bermond. If the weight of a subgraph is the number of its vertices, then the author proves that there always exists a cover with total weight $$c(n^ 2/\log n)$$ and this bound is best possible apart from a constant factor. This result is a corollary to a more general theorem of the paper which solves a complexity problem of T. G. Tarján.
Reviewer: F.Juhasz

##### MSC:
 05C70 Edge subsets with special properties (factorization, matching, partitioning, covering and packing, etc.) 05C35 Extremal problems in graph theory 05B20 Combinatorial aspects of matrices (incidence, Hadamard, etc.)
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##### References:
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