Perhaps you should try some spelling variations:
mittelbau » mittelbach
mittelbar » ermittelbar
mittelbare » ermittelbare, unmittelbaren
unmittelbare » unermittelbare, ununmittelbaren, ermittelbar
unmittelbar » unermittelbar

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((mittelbau OR (mittelbar OR (mittelbare OR unmittelbare))) OR unmittelbar).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((mittelbau or (mittelbar or (mittelbare OR unmittelbare))) or unmittelbar)".
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (mittelbar or (mittelbare OR unmittelbare))) or unmittelbar)*.