Recently I saw a comment / discussion on Stack Overflow about answers that just contains a link. A moderator told a rookie that they should improve their answer, as it just contained a link to a different site, I think it was a blog. The site did give a good answer to the question, but the argument was that SO should contain complete answers. That way SO would grow and contain knowledge even if the remote page disappeared.
Should we strive for the same here at photo.SE?
One example of this happening here is the question Is there a formula to calculate DOF? Two answers, both linking to remote resources.