Perhaps you should try some spelling variations:
investment series » investment services, investment barriers, investment treaties
investment period » investment policy, investment demand, adjustment period
fixed investment » direct investment
based investment » best investment, bond investment, related investment
kent based » agent based, test based

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: (( h. agent fixed investment series ) OR ( h. kent based investment period ))~.
• Adding a wildcard symbol may retrieve word variants: (( h. agent fixed investment series ) or ( h. kent based investment period ))*.