Perhaps you should try some spelling variations:
mittelbar » mittelbare, ermittelbar, unmittelbare
unmittelbar » unmittelbare, unermittelbar, ununmittelbare
ermittelbare » ermittelbaree, erermittelbare, erunmittelbaree, ermittelbar, unmittelbare, mittelbare
mittelbis » mittelbaus, mittelbau

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 ermittelbare) OR mittelbis).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((mittelbar OR unmittelbar) or ermittelbare) or mittelbis)".
• Adding a wildcard symbol may retrieve word variants: (((mittelbar OR unmittelbar) or ermittelbare) or mittelbis)*.