1. M. Eichler, Quadratische Formen und orthogonale Gruppen, Berlin 1952 (Chapter 1).
2. LetF be a finite dimensional, non-singular vectorspace,F 1 andF 2 two subspaces ofF of the same dimension. A necessary and sufficient condition that there exists an orthogonal transformation ofF 1 ontoF 2 is that the restrictions of the metric form onF toF 1 andF 2 are equivalent. See e.g.J. Dieudonné, Sur les groupes classiques. Paris 1958 (18).
3. See e.g.J. Dieudonné, loc. cit. (23).
4. See e.g.C. C. Chevalley, The Algebraic Theory of Spinors, New York 1955 (38).