Perhaps you should try some spelling variations:
international service » international overview, international justice, international science
international serious » international services, international religious, international settings
numerical mathematics » industrial mathematics, general mathematics
international series » international services, international serials, international aerien

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 serious))) OR (international service)) of ((numerical mathematics) OR (numerische mathematik)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((international series) OR (international serious))) or (international service)) of ((numerical mathematics) or (numerische mathematik))".
• Adding a wildcard symbol may retrieve word variants: ((((international series) OR (international serious))) or (international service)) of ((numerical mathematics) or (numerische mathematik))*.