Perhaps you should try some spelling variations:
mittelbau » mittelbach
mittelbar » unmittelbar, ermittelbar, unmittelbare
mittelbare » unmittelbare, ermittelbare, unmittelbaree, unmittelbaren
unermittelbar » unerunmittelbar, unerermittelbar, unerunmittelbare, unvermittelbar, 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 (mittelbar OR mittelbare)) OR (unermittelbar OR unermittelbar)).
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (mittelbar or mittelbare)) or (unermittelbar or unermittelbar))*.