Perhaps you should try some spelling variations:
mittelbau » mittelbare
mittelbach » mittelbare
mittelbar » mittelbare, unmittelbar, ermittelbar
unmittelbare » unmittelbaree, ununmittelbare, unermittelbare, unmittelbar, ermittelbar

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 (mittelbach OR mittelbar)) OR unmittelbare).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((mittelbau or (mittelbach OR mittelbar)) or unmittelbare)".
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (mittelbach OR mittelbar)) or unmittelbare)*.