| Sat, 23 Oct 2010 12:51:38 +0000 | wu | add some proofs about the other direction | file | diff | annotate |
| Fri, 22 Oct 2010 19:43:56 +0000 | urbanc | deleted two unnecessary lemmas | file | diff | annotate |
| Thu, 21 Oct 2010 15:06:30 +0000 | urbanc | tried at the end to prove the other direction (failed at the moment) | file | diff | annotate |