1. [1] G. Birkhoff and G.-C. Rota, Ordinary Differential Equations, 3rd ed., Wiley, New York, 1978.
2. [2] U. Brauer and L. Karp, Local existence of solutions of self gravitating relativistic perfect fluids, Comm. Math. Phys. 325 (2014), 105–141.
3. [3] R. S. Hamilton, The inverse function theorem of Nash and Moser, Bull. Amer. Math. Soc. (N.S.) 7 (1982), 65–222.
4. [4] M. Hukuhara, T. Kimura, and T. Matuda, Equations différentielles ordinaires du premier ordre dans le champ complexe, Publ. Math. Soc. Japan, Tokyo, 1961.
5. [5] L. D. Landau and E. M. Lifshitz, Course of Theoretical Physics, Vol. 2, 4th ed., Pergamon Press, Oxford, 1975.