I have seen the paper: W. Li and J.-X. Chen,
The eigenvalue perturbation bound for arbitrary matrices
, J. Comput.Math. (2006), 141–148 in this regard. Are there any more? Ren-Cang Li (2014). "Matrix Perturbation Theory". In Hogben, Leslie. Handbook of linear algebra (Second ed.) is another survey. Can anybody help me to have more on this topic?