Perhaps you should try some spelling variations:
comparative problem » comparative profile, collaborative problem, comparative promoter
cooperative problem » cooperative program, operative problems, cooperative project
relating concepts » relations concepts, rating concepts, regarding concepts
concepts citrus » concepts chris, concepts cited, concepts critiques

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

• Performing a fuzzy search may retrieve terms with similar spellings: international ((comparative problem) OR (cooperative problem)) relating concepts citrus~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "international ((comparative problem) OR (cooperative problem)) relating concepts citrus".
• Adding a wildcard symbol may retrieve word variants: international ((comparative problem) OR (cooperative problem)) relating concepts citrus*.