extra_*.lang files

[Frontcannon]

This is my first thread here where I need help! I'm currently writing a tutorial on the structure and inner workings of .lang files (something like this).

The problem is they aren't documented at all in the Wiki, so all I can grasp is what I read in the game's main .lang files..

I figured out how Messages, Examine-Areas and Notes work, but Item-Descriptions still don't show up in my test level.

So anyone here that could enlighten me? Any help is appreciated.