1. Introduction to Commutative Algebra;Atiyah,1969
2. Gauge-natural bundles and generalized gauge theories;Eck;Mem. Am. Math. Soc.,1981
3. Invariants of k-jet actions;Eck;Houston J. Math.,1984
4. Natural vector bundles;Epstein,1969
5. I. Moerdijk and G.E. Reyes, C∞-rings, Preprint, Université de Montréal.