Skibsted, E. & Derezinski, J. (2008). Classical scattering at low energies. In Perspectives in operator algebras and mathematical physics: conference proceedings, Bucharest, august 10-17, 2005 (pp. 51-83). Theta Foundation.
Kock, A. (2007). Principal bundles, groupoids, and connections. In J. Kubarski, J. Pradines, T. Rybicki & W. Robert (Eds.), Geometry and topology of manifolds: the mathematical legacy of Charles Ehresmann on the occasion of the hundredth anniversary of his birthday (pp. 185-200). Polish Academy of Sciences.