Perhaps you should try some spelling variations:
investment treaties » investment strategies, investment activities, investment incentives
based investment » fixed investment, best investment, bond investment
investment rate » investment climate
test based » text based, rest based, trust based
head fixed » heads mixed, here fixed

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( h. test based investment rate ) or ( h. ((road fixed) OR (head fixed)) investment treaties ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( h. test based investment rate ) OR ( h. ((road fixed) OR (head fixed)) investment treaties )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( h. test based investment rate ) or ( h. ((road fixed) OR (head fixed)) investment treaties ))".
• Adding a wildcard symbol may retrieve word variants: (( h. test based investment rate ) or ( h. ((road fixed) OR (head fixed)) investment treaties ))*.