Perhaps you should try some spelling variations:
ihren grenzgebieten » ihre grenzgebiete
ihrer grenzgebiete » ihre grenzgebiete, der grenzgebiete, deren grenzgebiete
model surveys » models survey, oder surveys, model survives
model survey » models survey, model surgery, modern survey
2c a » 12c a, 2 a, c a

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