Perhaps you should try some spelling variations:
mittelbau » mittelbar, mittelbare, mittelbach
ermittelbar » unmittelbar
ermittelbare » unmittelbare, mittelbare, vermittelbar
ununmittelbare » unmittelbare, unvermittelbare, unmittelbar

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 (ermittelbar OR ununmittelbare)) OR ermittelbare).
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (ermittelbar or ununmittelbare)) or ermittelbare)*.