Perhaps you should try some spelling variations:
"das original reference" » "das original references", "das original conference", "das origin references", "its original reference"
"his original reference" » "his original references", "his original conference", "his origin references"
"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 ("das regional reference"))) OR ("his original reference")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"das original reference\") OR (\"das regional reference\"))) or (\"his original reference\"))".
• Removing quotes may allow a broader search: (((( das original reference ) OR ( das regional reference ))) or ( his original reference )).
• Adding a wildcard symbol may retrieve word variants: (((("das original reference") OR ("das regional reference"))) or ("his original reference"))*.