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Critically indecomposable partially ordered sets, graphs, tournaments and other binary relational structures. (English) Zbl 0776.06002
The paper characterizes the critically indecomposable binary relational structures showing that for every odd order $$(\geq 5)$$ there are five and for every even order $$(\geq 6)$$ there are four of them (up to a certain type of equivalence). The classes of critically indecomposable posets, graphs, tournaments and digraphs are included as special cases. It is also shown that every indecomposable structure of order $$n+2$$ $$(n\geq 5)$$ has an indecomposable substructure of order $$n$$.

##### MSC:
 06A06 Partial orders, general 05C99 Graph theory 05C75 Structural characterization of families of graphs 05C70 Edge subsets with special properties (factorization, matching, partitioning, covering and packing, etc.) 05C20 Directed graphs (digraphs), tournaments
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##### References:
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