B. Aebischer a.o.: Symplectic geometry. BirkhŠuser 1994, 250p. 3-7643-5064-4. DM 68. 5020 R. Burckel: Inessential maps and classical euclidean topology. 2687 Chatterji/, 119-137. -2739 Ian Porteous: Topological geometry. Cambridge UP 1981. 2650 Lee Rudolph: The structure of orthogonal transformations. Am. Math. Monthly 98 (1991), 349-352. 1698 Ernst Snapper/Robert Troyer: Metric affine geometry. Dover 1971.