Perhaps you should try some spelling variations:
"state vector" » "space vector"
"state sector" » "estate sector", "state vectors", "state section"
"state actor" » "state action", "state after", "state acts"
"state actors" » "state actions", "state afters", "state actss", "state factors"

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 ("state vector"))) OR ("state sector"))) OR ("state actors")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((\"state actor\") OR (\"state vector\"))) or (\"state sector\"))) or (\"state actors\"))".
• Removing quotes may allow a broader search: (((((( state actor ) OR ( state vector ))) or ( state sector ))) or ( state actors )).
• Adding a wildcard symbol may retrieve word variants: (((((("state actor") OR ("state vector"))) or ("state sector"))) or ("state actors"))*.