1. R. Dahm, Yad. Fiz. 73, 297 (2010) [Phys. Atom. Nucl. 73, 276 (2010)].
2. R. Dahm, Yad. Fiz. 75, 1244 (2012) [Phys. Atom. Nucl. 75, 1173 (2012)]; http://arXiv.org/abs/1102. 0027.
3. R. Dahm, arXiv:1508.06872, submitted to Adv. Appl. Clifford Algebras.
4. F. Klein, Vorlesungen über nicht-euklidische Geometrie (Springer-Verlag, Berlin, Heidelberg, 1928).
5. R. Gilmore, Lie Groups, Lie Algebras and Some of Their Applications (Wiley, New York, 1974).