Perhaps you should try some spelling variations:
mittelbar » mittelbare, unmittelbar
unmittelbare » unmittelbaree, ununmittelbare, unmittelbar
ermittelbar » ermittelbare, erunmittelbar, unmittelbar
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 unmittelbare) OR ermittelbar) OR mittelbisau)*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((mittelbar OR unmittelbare) or ermittelbar) or mittelbisau)*".