[1] J. A. Dieudonni J. B. Carrel: 
Invariant Theory. Old and New, Academic Press, New York-London 1971. 
MR 0279102[2] J. Janyška: 
Geometrical properties of prolongation functors. Časopis pěst. mat. 110 (1985), 77-86. 
MR 0791280[3] G. Kainz P. Michor: 
Natural transformations in differential geometry. Czechoslovak Math. J. 37 (112) (1987), 584-607. 
MR 0913992[4] T. Klein: 
Connections on higher order tangent bundles. Časopis pěst. mat. 106 (1981), 414-421. 
MR 0637822 | 
Zbl 0497.58003[5] I. Kolář: 
Some natural operators in differential geometry. Proc. Conf. Differential Geometry and its Applications, Brno 1986, D. Reidel, 1987, 91-110. 
MR 0923346[6] I. Kolář G. Vosmanská: 
Natural operations with second order jets. Rendiconti del Circolo Matematico di Palermo, Serie II. numero 14-1987, 179-186. 
MR 0920854[7] R. S. Palais C. L. Terng: 
Natural bundles have finite order. Topology, 16 (1977), 271-277. 
MR 0467787[9] G. Vosmanská: Natural transformations of jet spaces. Thesis (Czech), Brno 1987.