1. G. Birkhoff, J. von Neumann, Ann. Math., second series 37, 823–843 (1936)
2. C. Piron, Helv. Phys. Acta 37, 439–468 (1964)
3. M.P. Solèr, Commun. Algebra 23, 219–243 (1995)
4. S.S. Holland, Bull. Am. Math. Soc. 32, 205–234 (1995)
5. E.C.G. Stueckelberg, Helv. Phys. Acta 32, 254 (1959)