Perhaps you should try some spelling variations:
international serious » international services, international religious, international settings
numerical mathematics » general mathematics, numerische mathematik
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)) of ((((numerical mathematics) OR (industrial mathematics))) OR (numerische (mathematik OR mathematical))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((international series) OR (international serious)) of ((((numerical mathematics) or (industrial mathematics))) or (numerische (mathematik or mathematical)))".
• Adding a wildcard symbol may retrieve word variants: ((international series) OR (international serious)) of ((((numerical mathematics) or (industrial mathematics))) or (numerische (mathematik or mathematical)))*.