Perhaps you should try some spelling variations:
international convention » international cooperation, international context, international communication
objective formulation » objective formation, injective formulations, objective formations
objective foundation » objective function, objective formation, objective functions
classes citrus » causes citrus, assess citrus, classes irks

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: international convention ((objective foundation) OR (objective formulation)) classes citrus~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "international convention ((objective foundation) OR (objective formulation)) classes citrus".
• Adding a wildcard symbol may retrieve word variants: international convention ((objective foundation) OR (objective formulation)) classes citrus*.