Messirdi, Sofiane, et al. “A New Representation of Left and Right Generalized Drazin Invertible Operators”. Methods of Functional Analysis and Topology, vol. 27, no. 1, Mar. 2021, pp. 37-43, https://doi.org/https://doi.org/10.31392/MFAT-npu26_1.2021.06.