1. Atiyah, M.F., Bott, R., Shapiro, A.: Clifford modules. Topology 3((suppl, suppl. 1)), 3–38 (1964)
2. Baez, J.C.: The octonions. Bull. Am. Math. Soc. (N.S.) 39(2), 145–205 (2002)
3. Cartan, H., Eilenberg, S.: Homological Algebra. Princeton Landmarks in Mathematics. Princeton University Press, Princeton (1999). With an appendix by David A. Buchsbaum, Reprint of the 1956 original
4. Colombo, F., Sabadini, I., Struppa, D.C.: Noncommutative Functional Calculus, Progress in Mathematics, vol. 289. Birkhäuser/Springer Basel AG, Basel (2011). Theory and applications of slice hyperholomorphic functions
5. Eilenberg, S.: Extensions of general algebras. Ann. Soc. Polon. Math. 21, 125–134 (1948)