I would like to know some reference (articles, books...) about any kind of moduli spaces of any of the following objects:
over singular algebraic curves (reducible or not), in any of the following frameworks:
algebraic geometry (in characteristic zero and in positive characteristic)
...anything you like...
I would be particularly glad to have some reference about torsion-free sheaves in the algebro-geometric setting.
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).