Looking for writings about lifted and unlifted types, I stumbled upon this page called Informal Semantics. It looks like it has belonged to the GHC user guide some while ago. But I could not find it in the later versions of the guide.
Looking at the history of the GHC repository, I see that the commit 5bf22f06ef71f61094de7564dee770f136d5481a Remove external core
(dated back at 2014) removed this page.
What happened?