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

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 unmittelbare)) OR mittelbisau).
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (mittelbar or unmittelbare)) or mittelbisau)*.