Perhaps you should try some spelling variations:
international materials » international trials, international serials, international nanomaterials
numerical mathematics » industrial mathematics, general mathematics
mathematik » mathematical

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