Perhaps you should try some spelling variations:
mathematical union » mathematical function, mathematical question, mathematical solution
mathematical und » mathematica und, mathematical using, mathematical user
der grenzgebiete » die grenzgebiete, dem grenzgebiet, ihre grenzgebiete
modeling survey » modeling supply, models survey, modeling survival
model survey » models survey, model surgery, modern 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 ((mathematical und) OR (mathematical union)) der grenzgebiete. 2. folge, a series of ((model survey) OR (modeling survey)) in mathematics.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ergebnisse der ((mathematical und) OR (mathematical union)) der grenzgebiete. 2. folge, a series of ((model survey) or (modeling survey)) in mathematics".
• Adding a wildcard symbol may retrieve word variants: ergebnisse der ((mathematical und) OR (mathematical union)) der grenzgebiete. 2. folge, a series of ((model survey) or (modeling survey)) in mathematics*.