Two-fold completeness of root vectors of
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Yakov Yakubov
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Article
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2005
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Elsevier Science
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English
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We consider a spectral problem for a system of second order (in the spectral parameter) abstract pencils in a Hilbert space and prove the completeness and the Abel basis property of a system of eigenvectors and associated vectors. In some special cases, we obtain the expansion of vectors with respec