1. Abramovich Y.A., Aliprantis C.D.: An invitation to operator theory, Graduate Studies in Mathematics, vol. 50. American Mathematical Society, Providence, RI (2002)
2. Androulakis G., Popov A.I., Tcaciuc A., Troitsky V.G.: Almost invariant half-spaces of operators on Banach spaces. Integral Equ. Oper. Theory 65(4), 473–484 (2009)
3. Radjavi H., Rosenthal P.: Invariant Subspaces, 2nd edn. Dover Publications, Inc., Mineola, NY (2003)