Perhaps you should try some spelling variations:
mittelbar » unmittelbar, ermittelbar, unmittelbare
ununmittelbare » unununmittelbare, ununermittelbare, unununmittelbaree, unmittelbare, unvermittelbare, unmittelbar
unununmittelbare » ununununmittelbare, unununermittelbare, ununununmittelbaree, ununmittelbare, ununvermittelbare, ununmittelbar, bundesunmittelbare, unmittelbare, sachunmittelbare
mittelbare » unmittelbare, ermittelbare, unmittelbaree
unmittelbaren » ununmittelbaren, unermittelbaren, ununmittelbareen, unmittelbare, 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: ((mittelbach OR ((mittelbar OR ((ununmittelbare OR unununmittelbare) OR (ununmittelbare OR unununmittelbare))) OR mittelbare)) OR unmittelbaren).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((mittelbach or ((mittelbar or ((ununmittelbare OR unununmittelbare) or (ununmittelbare OR unununmittelbare))) or mittelbare)) or unmittelbaren)".
• Adding a wildcard symbol may retrieve word variants: ((mittelbach or ((mittelbar or ((ununmittelbare OR unununmittelbare) or (ununmittelbare OR unununmittelbare))) or mittelbare)) or unmittelbaren)*.