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

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 observatory) OR (economique 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 observatory) or (economique internationale))*".