Perhaps you should try some spelling variations:
numerische mathematical » numerical mathematical, numerischen mathematik, numerical mathematics
international service » international overview, international justice, international science
international series » international services, international serious, international serials

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: ((international series) OR (international service)) of ((numerische mathematik) OR (numerische mathematical)).
• Adding a wildcard symbol may retrieve word variants: ((international series) or (international service)) of ((numerische mathematik) or (numerische mathematical))*.