I get you now, I misunderstood. You mean the links to other people's websites are broken. I thought you meant DOW internal links.
Yes, I see that now, and they're fixed.
The Beaver Energy site appears to be gone, so yes it 404s. International Supply redid their website, and didn't bother to redirect the old links (I updated the link). The others are email addresses, you may not have an email client set up to handle them. No website anyways.
Sorry for the confusion!