Reference for principal bundles and related concepts I am looking for a good reference for fibre bundles on differential manifolds, Ehresmann connections, principal $G$-bundles and principal Ehresmann connections (the $G$-equivariant version of Ehresmann connections). Could anyone advise me on this? I have looked at the book Fibre Bundles by Hausmöller, but it isn't quite what I want.
Thanks in advance.

Late to the party, but: Chapter 6 in Loring Tu's Differential Geometry: Connections, Curvature, and Characteristic Classes seems friendly enough, and well explained. I think sections §27 and §28 are what you're looking for.
