@article{hartwig_wang_wei_2001, title={Some additive results on Drazin inverse}, volume={322}, ISSN={["1873-1856"]}, DOI={10.1016/S0024-3795(00)00257-3}, abstractNote={Some additive perturbation results for Drazin inverses are given. In particular, a formula is given for the Drazin inverse of a sum of two matrices, when one of the products of these matrices vanishes. Some special applications of this are also considered.}, number={1-3}, journal={LINEAR ALGEBRA AND ITS APPLICATIONS}, author={Hartwig, RE and Wang, GR and Wei, YM}, year={2001}, month={Jan}, pages={207–217} }
 @article{wei_wang_1997, title={The perturbation theory for the drazin inverse and its applications}, volume={258}, number={1997 June}, journal={Linear Algebra and Its Applications}, author={Wei, Y.-M. and Wang, G. R.}, year={1997}, pages={179–186} }