Perhaps you should try some spelling variations:
mittelbau » mittelbach
mittelbar » unmittelbare
mittelbare » unmittelbaree, unmittelbare, unmittelbaren
ermittelbar » erunmittelbare
unmittelbar » ununmittelbare

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 ermittelbar))) OR unmittelbar).
• Adding a wildcard symbol may retrieve word variants: ((mittelbau or (mittelbar or (mittelbare or ermittelbar))) or unmittelbar)*.