Perhaps you should try some spelling variations:
"methode literatur" » "methoden literatur", "methods literature", "befunde literatur"
"werden literatur" » "boden literatur", "den literatur", "methoden literatur"
"erde literatur" » "befunde literatur", "absurde literatur"

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: (((("erde literatur") OR ("werden literatur"))) OR ("methode literatur")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"erde literatur\") OR (\"werden literatur\"))) or (\"methode literatur\"))".
• Removing quotes may allow a broader search: (((( erde literatur ) OR ( werden literatur ))) or ( methode literatur )).
• Adding a wildcard symbol may retrieve word variants: (((("erde literatur") OR ("werden literatur"))) or ("methode literatur"))*.