Perturbation theorems for the joint spectrum of commuting matrices: a conservative approach

Elsner L. Perturbation theorems for the joint spectrum of commuting matrices: a conservative approach. Linear algebra and its applications. 1994;208-209:83-95.It is shown that recent perturbation theorems for the joint spectrum of commuting matrices, which have been proved using Clifford-algebra tools, can be obtained and improved by classical means, as used in the case of the standard eigenvalue problem