1. The discussion of stellar stability, just as the interpretation of intrinsic stellar variability, rests for a good part on the theory of small oscillations so that, we shall often have the occasion to refer to: Ledoux, P., and Th. Walraven: Variable Stars. In this volume.
2. Wavre, R.: Figures Planétaires et Géodésie. Paris: Gauthier-Villars 1932.
3. Duiiem, P.: Traité d’énergétique, 2 Vol. Paris: Gauthier-Villars 1911. (The transition from a discrete to a continuous system is discussed in Vol. II, Chap. XVI, § 6, p. 304 ).
4. For a recent and generally excellent summary of the most significant results including those of E. Cartan on the dynamical stability of the Jacobi series, cf.:
5. a) Lyttleton, R. A.: The Stability of Rotating Liquid Masses. Cambridge 1953.