U. Jannsen, S. Kleiman and J.-P. Serre, Motives, Proceedings of the AMS-IMS-SIAM Joint Summer Research Conference held at the University of Washington, Seattle, Washington, July 20â€“August 2, 1991. Proceedings of Symposia in Pure Mathematics 55, part 1 and 2. American Mathematical Society, Providence, RI, 1994.

The fact that the category of numerical motives is semisimple abelian is in