1. Atiyah, M. F.:K-theory, New York-Amsterdam: Benjamin 1967
2. Berstein, I., Ganea, T.: The Category of a Map and of a Cohomology Class. Fundamenta Math.50, 265?279 (1961/62)
3. Borel, A.: Sur la cohomologie des espaces fibrés principaux et des espaces homogènes de groupes de Lie compacts, Ann. of Math., II. Ser.57, 115?207 (1953)
4. Browder, F. E.: Nonlinear Eigenvalue Problems and Group Invariance. In: Functional Analysis and Related Fields (Chicago 1968), (ed. by F. E. Browder); pp. 1?58. Berlin-Heidelberg-New York: Springer 1970
5. Dieudonné, J.: Eléments d'Analyse, Tome 3, Paris: Gauthier-Villars 1970