Perhaps you should try some spelling variations:
original references » origin references, origins references, marginal references
signals references » minerals references, pitfalls references, symbols references
goals references » tools references, soils references, models references
einer original » eines originals, either original, ein original

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: (( einer original references ) OR ( clear ((signals references) OR (goals references)) )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( einer original references ) or ( clear ((signals references) OR (goals references)) ))".
• Adding a wildcard symbol may retrieve word variants: (( einer original references ) or ( clear ((signals references) OR (goals references)) ))*.