1. E. Angelopoulos, M. Flato, C. Fronsdal and D. Sternheimer, Massless particles, conformal group and De Sitter universe, Phys. Rev. D23 (1981), 1278–1289.
2. P. Bonneau, M. Gerstenhaber, A. Giaquinto and D. Sternheimer, Quantum groups and deformation quantization: explicit approaches and implicit aspects, J. Math. Phys. 45 (2004), no. 10, 3703–3741.
3. S. Coleman and J. Mandula, All possible symmetries of the S matrix, Phys. Rev. 159 (1967), 1251–1256.
4. A. Connes, Noncommutative Geometry, Academic Press, San Diego 1994.
5. A. Connes, 2006 Lectures at Collège de France and related material posted on http://www.alainconnes.org/downloads.html