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{\bf Jan Ekstein }
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{\bf Hamiltonian Cycles in the Square of a Graph}
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We show that under certain conditions the square of the graph obtained by identifying
a vertex in two graphs with hamiltonian square is also hamiltonian. Using this
result, we prove necessary and sufficient conditions for hamiltonicity of the square
of a connected graph such that every vertex of degree at least three in a~block graph
corresponds to a cut vertex and any two these vertices are at distance at least four.
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