Perhaps you should try some spelling variations:
international astronomical » international economics
politique internationale » policy international
astronomy observational » astronomy observations, astronomy observatory, astronomical observations
international economic » international economics

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 astronomical) OR (international economic))) OR (observations astronomical)) union/union ((astronomy observational) OR (politique internationale)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((international astronomical) OR (international economic))) or (observations astronomical)) union/union ((astronomy observational) or (politique internationale))".
• Adding a wildcard symbol may retrieve word variants: ((((international astronomical) OR (international economic))) or (observations astronomical)) union/union ((astronomy observational) or (politique internationale))*.