You may have seen all of these, but in case they are helpful (none are as complete as one would like): http://arxiv.org/abs/hep-th/9409195 http://arxiv.org/abs/math.DG/0603190 http://books.google.com/books?id=kP...pg=PA383&ots=PDipqKbFz_&dq=kriele+singularity This is where such a thing hopefully will be in the future (but now is just a stub): http://www.scholarpedia.org/article/Hawking-Penrose_singularity_theorems