Perhaps you should try some spelling variations:
cluster surveys » cluster survey, customer surveys, cluster services
user surveys » use surveys, user survey, based surveys
od surveys » old surveys, 4d surveys, ed surveys
d surveys » _ surveys, 1 surveys, d survey

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 und im grenzgebiet. 2. folge, a series of ((((od surveys) OR (((user surveys) OR (cluster surveys))))) OR (d surveys)) in mathematics.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ergebnisse der mathematik und im grenzgebiet. 2. folge, a series of ((((od surveys) or (((user surveys) OR (cluster surveys))))) or (d surveys)) in mathematics".
• Adding a wildcard symbol may retrieve word variants: ergebnisse der mathematik und im grenzgebiet. 2. folge, a series of ((((od surveys) or (((user surveys) OR (cluster surveys))))) or (d surveys)) in mathematics*.