Perhaps you should try some spelling variations:
international services » international service, international reserves, integration services
numerical mathematics » industrial mathematics, general mathematics
international trials » international tribunals, interventional trials, international trade

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 services) OR (international trials)) of ((numerical mathematics) OR (numerische mathematik)).
• Adding a wildcard symbol may retrieve word variants: ((international services) or (international trials)) of ((numerical mathematics) or (numerische mathematik))*.