Perhaps you should try some spelling variations:
der mathematical » her mathematical, mer mathematical, order mathematical
cover surveys » care surveys, other surveys, user surveys
oder surveys » der surveys, other surveys, user surveys

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 mathematical ((((und ihrer) OR (und ihr))) OR (und ihre)) grenzgebiete. 2. folge, a series of ((oder surveys) OR (cover surveys)) in mathematics.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ergebnisse der mathematical ((((und ihrer) OR (und ihr))) or (und ihre)) grenzgebiete. 2. folge, a series of ((oder surveys) or (cover surveys)) in mathematics".
• Adding a wildcard symbol may retrieve word variants: ergebnisse der mathematical ((((und ihrer) OR (und ihr))) or (und ihre)) grenzgebiete. 2. folge, a series of ((oder surveys) or (cover surveys)) in mathematics*.