Perhaps you should try some spelling variations:
mittelbar » mittelbare, unmittelbar, unmittelbare
ermittelbar » ermittelbare, erunmittelbar, erunmittelbare, unmittelbar
mittelbisau » mittelbis
mittelbau » mittelbare, mittelbach

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 ermittelbar) OR (mittelbisau OR mittelbau))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((mittelbar or ermittelbar) or (mittelbisau OR mittelbau))*".