1. Byrnes, G.B.: A complete set of Bianchi identities for tensor fields along the tangent bundle projection. J. Phys. A Math. Gen. 27, 6617–6632 (1994)
2. Chern, S.-S.: Sur la géométrie d’un système d’équations différentielles du second ordre. Bull. Sci. Math. 63, 206–212 (1939)
3. Crampin, M., Martínez, E., Sarlet, W.: Linear connections for systems of second-order ordinary differential equations. Ann. Inst. H. Poincaré Phys. Théor. 65(2), 223–249 (1996)
4. Kosambi, D.D.: Systems of differential equations of the second order. Quart. J. Math. Oxford 6, 1–12 (1935)
5. Kumpera, A.: Invariants différentiels d’un pseudogroupe de Lie. I, II. J. Diff. Geom. 10, 289–345, 347–416 (1975)