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has been cited by the following article:

• TITLE: Spectra of 2 × 2 Upper-Triangular Operator Matrices

  AUTHORS: Haiyan Zhang

  KEYWORDS: Spectra; Upper-Triangular Operator Matrix; Fredholm Operator

  JOURNAL NAME: Applied Mathematics, Vol.4 No.11A, October 31, 2013

  ABSTRACT: In [Perturbation of Spectrums of 2 × 2 Operator Matrices, Proceedings of the American Mathematical Society, Vol. 121, 1994], the authors asked whether there was an operator such that for a given pair(A,B)of operators, where the operator was defined by . In this note, a partial answer for the question is given.