Celebratio Mathematica

Y. Cho­quet-Bruhat and T. Rug­geri: “Hy­per­bol­i­cité du système \( 3+1 \) des équa­tions d’Ein­stein,” C. R. Acad. Sci. Par­is Sér. I Math. 294 : 12 (1982), pp. 425–​429. An Eng­lish ver­sion of the French ori­gin­al ap­peared in Comm. Math. Phys. 89: 2 (1983). MR 659737 article

Y. Cho­quet-Bruhat and T. Rug­geri: “Hy­per­bol­i­city of the \( 3+1 \) sys­tem of Ein­stein equa­tions,” Comm. Math. Phys. 89 : 2 (1983), pp. 269–​275. This ap­pears to be an Eng­lish ver­sion of the French art­icle of the same title pub­lished a year earli­er in C. R. Acad. Sci. Par­is Sér. I Math. 294:12 (1982). MR 709467 Zbl 0521.​53034 article