Perhaps you should try some spelling variations:
mittelbau » mittelbare, mittelbach
mittelbar » mittelbare, ermittelbar
unmittelbar » unmittelbare, unermittelbar
unmittelbare » unmittelbaree, unermittelbare, 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 (unmittelbar OR unmittelbare))) OR mittelbisau).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((mittelbau or (mittelbar or (unmittelbar OR unmittelbare))) or mittelbisau)".
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (mittelbar or (unmittelbar OR unmittelbare))) or mittelbisau)*.