I would like to know some reference (articles, books...) about any kind of moduli spaces of any of the following objects:

vector bundles

torsion-free sheaves

principal bundles

parabolic bundles

over *singular* algebraic curves (reducible or not), in any of the following frameworks:

algebraic geometry (in characteristic zero and in positive characteristic)

holomorphic geometry

integrable systems

gauge theory

differential geometry

topology

...anything you like...

I would be particularly glad to have some reference about torsion-free sheaves in the algebro-geometric setting.

Thanks

**Edit:** I should emphasize that my reference request is about some structures over **singular** curves. The freedom I expect in a typical answer should be on the structure (e.g. bundles, torsion-free sheaves,...) and on the viewpoint (e.g. pure algebraic geometry, trascendental methods, ...), but the base curve must be singular (for the answer not to be offtopic).

singular(projective) algebraic curve. – Qfwfq Apr 8 '10 at 16:37"semistable". – Qfwfq Apr 8 '10 at 17:19