Betcke, T;    Kressner, D;      (2011)    Perturbation, extraction and refinement of invariant pairs for matrix polynomials.                   Linear Algebra and its Applications , 435  (3)   pp. 514-536.    10.1016/j.laa.2010.06.029 <https://doi.org/10.1016/j.laa.2010.06.029>.       Green open access