1. The rotation of eigenvectors by a perturbation;Davis;J. Math. Anal. Appl.,1963
2. Perturbation theory for linear operators;Kato,1966
3. Similarity and interpolation between projectors;Kovarik;Acta Sci. Math. (Szeged),1977
4. Manifolds of linear involutions;Kovarik;Linear Algebra and Appl.,1979
5. Manifolds of projector frames;Kovarik,1978