[OL]Proper way to note cities and regions

What is the proper way to write the location your relatives are from?

Mine are from Feldhausen which is in Langwarden Parish - Butjadingen region - Grandduchy of Oldenburg, Germany.
What would be the proper way to note this location in my genealogy records?

Can anyone refresh me as to when Oldenburg was a Duchy vs a Grandduchy, etc?

Thanks,

Rita