• Korean Journal of Mathematics
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• v.5 no.1
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• pp.9-16
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• 1997

In this paper, we construct new classes from the idea of [6, Theorem 2.1] and show that the property of operators belonging to the classes is inherited by certain dilations. And we also prove that the existence of common noncyclic vectors for certain families is equivalent to the existence of infinite dimensional common semi-invariant subspace of operators.