[1] C. Ehresmann: Les prolongements d'un espace fibré différentiable. C. R. Acad. Sci. Paris, 240(1955), 1755-1757. MR 0071083 | Zbl 0064.17502

[2] H. Goldschmidt S. Sternberg: The Hamilton formalism in the calculus of variations. Ann. Inst. Fourier (Grenoble), 23 (1973), 203-267. MR 0341531

[3] I. Kolář: On the prolongations of geometric object fields. An. Sti. Univ. "A1. I. Cuza" Iasj, 77(1971), 437-446. MR 0305278

[4] D. Krupka: A geometric theory of ordinary first order variational problems in fibered mani- folds. L, J. Math. Anal. Appl., 49 (1975), 180-206. MR 0362397

[5] A. Kumpera D. Spencer: Lie equations, I. Annals of Mathematics Studies 73, Princeton 1972.

[6] A. Kumpera: Invariants differentiels d'un pseudogroupe de Lie. I., J. Differential Geometry, 70(1975), 289-345. MR 0407911 | Zbl 0346.58012

[7] J. Pradines: Théorie de Lie pour les groupoldes différentiables. Calcul differentiel dans la catégorie des groupoldes infinitéimaux, C R. Acad. Sci. Paris 264 (1967) A, 245-248. MR 0216409

[8] Ngo van Que: Sur Pespace de prolongement differentiable. J. Differential Geometry, 2 (1968), 33-40. MR 0235587

[9] Ngo van Que: Nonabelian Spencer cohomology and deformation theory. J. Differential Geometry, 3 (1969), 165-211. MR 0266257 | Zbl 0206.50403