Perhaps you should try some spelling variations:
ihre grenzgebiete » ihren grenzgebieten, im grenzgebiet, und grenzgebiete
die grenzgebiete » im grenzgebiet, und grenzgebiete, die teilgebiete
models surveys » model survey, modern survey, modest survey
models survey » modeling survey, models supply
12c a » 12c _

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: %ergebnisse der (mathematik OR mathematical) und ((ihre grenzgebiete) OR (die grenzgebiete)). 2. folge%12c a series of ((models surveys) OR (models survey)) in mathematics%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%ergebnisse der (mathematik or mathematical) und ((ihre grenzgebiete) OR (die grenzgebiete)). 2. folge%12c a series of ((models surveys) or (models survey)) in mathematics%22".
• Adding a wildcard symbol may retrieve word variants: %ergebnisse der (mathematik or mathematical) und ((ihre grenzgebiete) OR (die grenzgebiete)). 2. folge%12c a series of ((models surveys) or (models survey)) in mathematics%22*.