Perhaps you should try some spelling variations:
mittelbar » mittelbare, ermittelbar, unmittelbare
unmittelbar » unmittelbare, unermittelbar, ununmittelbare
unmittelbaree » unmittelbareee, unermittelbaree, ununmittelbareee, unmittelbare, unmittelbaren, unmittelbarer
mittelbisau » mittelbau, 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: ((mittelbar OR (unmittelbar OR (unmittelbaree OR unmittelbaree))) OR mittelbisau).
• Adding a wildcard symbol may retrieve word variants: ((mittelbar or (unmittelbar or (unmittelbaree or unmittelbaree))) or mittelbisau)*.