Hello Dani
A lot of my OOB work comes from
world war 2 data book by john ellis
slaughter house by Kieth e bonn
German ground forces by D Glantz
several opsrey books dealing with axis and soviet units and numbers
Axis history web site
feldgrau web site
ww2 web site
https://www.ww2-weapons.com/germany-army...n-1939-41/
Plus other web sources...
BUT
they do not cover corp or Army unit attachments as you asked. I have tried to find a source for this information, but to no avail.
But I do not give up that quick!!
What I have been working on is a list of what would normally be standard attachments ie
artillery
Stug Btn
Heavy tank Btn
Pioneer Btn
Flak Btn Etc, Ect
Then going into the web sites & books, and going through all the units one by one. so I can get a fix on where they were and what corp they were in.
This web site for example.
http://www.lexikon-der-wehrmacht.de/Glie...ArtDiv.htm
If you scroll down it shows artillery div 18 for example. was with the 24 corp in Jan, attached to 4 panzer army in 1944 army group south (plus a lot of others can be traced).
I also read a lot. and note down where units are mentioned and cross check with the above sources.
I'm currently working on OOB's for all the separate army groups (south from 43-45) so reading a lot of rolf hinze.
Craig