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1. • CommentRowNumber1.
   • CommentAuthorMike Shulman
   • CommentTimeSep 8th 2015
   • PermaLink
   Author: Mike Shulman
   Format: MarkdownItexI thought I remembered some discussion at some point of "co-concrete objects", those for which $\flat A \to A$ is surjective. But now I can't find it on the lab or the forum. Is my memory faulty?

   I thought I remembered some discussion at some point of “co-concrete objects”, those for which $\flat A \to A$ is surjective. But now I can’t find it on the lab or the forum. Is my memory faulty?

2. • CommentRowNumber2.
   • CommentAuthorUrs
   • CommentTimeSep 8th 2015
   • (edited Sep 8th 2015)
   • PermaLink
   Author: Urs
   Format: MarkdownItexmaybe _[[co-concrete object]]_? [edit: I just went and fixed an evident typo there, and I have made "coconcrete object" redirect to the entry]

   maybe co-concrete object?

   [edit: I just went and fixed an evident typo there, and I have made “coconcrete object” redirect to the entry]

3. • CommentRowNumber3.
   • CommentAuthorMike Shulman
   • CommentTimeSep 8th 2015
   • PermaLink
   Author: Mike Shulman
   Format: MarkdownItexThanks. Apparently with the hyphen it doesn't turn up in search.

   Thanks. Apparently with the hyphen it doesn’t turn up in search.

4. • CommentRowNumber4.
   • CommentAuthorTodd_Trimble
   • CommentTimeSep 8th 2015
   • PermaLink
   Author: Todd_Trimble
   Format: MarkdownItexI wonder to what extent hyphenation turns up glitches? Recently I wrote [[Chu-Vandermonde identity]] but the link from here didn't work. Testing it now, it still doesn't, although I can force the issue by a copy-and-paste: see [here](http://ncatlab.org/nlab/show/Chu%E2%80%93Vandermonde+identity).

   I wonder to what extent hyphenation turns up glitches? Recently I wrote Chu-Vandermonde identity but the link from here didn’t work. Testing it now, it still doesn’t, although I can force the issue by a copy-and-paste: see here.

5. • CommentRowNumber5.
   • CommentAuthorUrs
   • CommentTimeSep 8th 2015
   • (edited Sep 8th 2015)
   • PermaLink
   Author: Urs
   Format: MarkdownItex...

   …

6. • CommentRowNumber6.
   • CommentAuthorUrs
   • CommentTimeSep 8th 2015
   • (edited Sep 8th 2015)
   • PermaLink
   Author: Urs
   Format: MarkdownItexTodd, that's the hyphen bug, first discussed [here](http://nforum.ncatlab.org/discussion/4567/hyphens-in-page-names-and-broken-links/). The workaround that I apply whenever I see the bug is this: I copy-and-paste the text of the grayed-link-that-ought-to-work into a redirect in the entry. To the naked eye this will look exactly like the entry title or like existing redirects, but I suppose internally the hyphen sometimes gets represented by different codes. [edit: Hm, actually in the case you point to the two hyphens do look different, even to the naked eye. In that case it's not a bug, just a nuisance. But just earlier today I saw the actual bug elsewhere, it's still there, too. In any case, hyphens require special attention.]

   Todd, that’s the hyphen bug, first discussed here.

   The workaround that I apply whenever I see the bug is this: I copy-and-paste the text of the grayed-link-that-ought-to-work into a redirect in the entry.

   To the naked eye this will look exactly like the entry title or like existing redirects, but I suppose internally the hyphen sometimes gets represented by different codes.

   [edit: Hm, actually in the case you point to the two hyphens do look different, even to the naked eye. In that case it’s not a bug, just a nuisance. But just earlier today I saw the actual bug elsewhere, it’s still there, too. In any case, hyphens require special attention.]

7. • CommentRowNumber7.
   • CommentAuthorTodd_Trimble
   • CommentTimeSep 8th 2015
   • PermaLink
   Author: Todd_Trimble
   Format: MarkdownItexUrs, thanks for the info. I also saw that the hyphens looked different, but saw nothing I did that would account for that. I'll remember your workaround, but also note that ordinarily I say [[Vandermonde identity]] or [[Vandermonde convolution identity]] anyway, so this particular case is no big deal.

   Urs, thanks for the info. I also saw that the hyphens looked different, but saw nothing I did that would account for that.

   I’ll remember your workaround, but also note that ordinarily I say Vandermonde identity or Vandermonde convolution identity anyway, so this particular case is no big deal.