Perhaps you should try some spelling variations:
"das original reference" » "das original references", "das original conference", "das origin references", "his original reference"
"its original reference" » "its original references", "its original conference", "its origin references", "its origin reference", "his original reference"
"das regional reference" » "das regional conference", "das regional differences", "das regional resilience", "das regionale reference", "gas regional reference", "dawns regional reference"

Try widening your search to All Fields.

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: (((("das original reference") OR ("its original reference"))) OR ("das regional reference")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"das original reference\") OR (\"its original reference\"))) or (\"das regional reference\"))".
• Removing quotes may allow a broader search: (((( das original reference ) OR ( its original reference ))) or ( das regional reference )).
• Adding a wildcard symbol may retrieve word variants: (((("das original reference") OR ("its original reference"))) or ("das regional reference"))*.