Perhaps you should try some spelling variations:
"estate sector" » "state section"
"state vector" » "space vector"
"state action" » "state reactions", "state actors"
"state actor" » "state actors", "state sector", "state after"

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: (((("state actor") OR ((("estate sector") OR ("state vector"))))) OR ("state action")).
• Removing quotes may allow a broader search: (((( state actor ) or ((( estate sector ) or ( state vector ))))) or ( state action )).
• Adding a wildcard symbol may retrieve word variants: (((("state actor") or ((("estate sector") or ("state vector"))))) or ("state action"))*.