Katavolos A, Papanastassiou N.
Order convergence in operator algebras. Math. Balkanica (N.S.). 1991;5:245–249.
Katavolos A.
Decomposability of operators relative to two subspaces. In: Selfadjoint and nonselfadjoint operator algebras and operator theory ({F}ort {W}orth, {TX}, 1990). Vol. 120. Amer. Math. Soc., Providence, RI; 1991. pp. 77–81.
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