1. E. Artin,Geometric Algebra, New York: Interscience, 1957; reprinted by Wiley, New York, 1988.
2. H. Aslaksen,SO(2) invariants of a set of 2 x 2 matrices.Math. Scand. 65 (1989), 59–66.
3. H. Aslaksen, E.-C. Tan, and C. Zhu, Invariant theory of special orthogonal groups,Pacific ]. Math. (in press).
4. A. Bagazgoitia, A determinantal identity for quaternions, inProceedings of 1983 Conference on Algebra Lineal y Aplicaciones, Vitoria-Gasteiz, Spain, 1984, pp. 127–132.
5. R. W. Barnard and E. Hastings Moore,General analysis. Part 1, Memoirs of the American Philosophical Society, 1935.