Perhaps you should try some spelling variations:
"state vectors" » "state detectors", "space vectors"
"state sector" » "estate sector", "state section", "state sensor"
"state vector" » "space vector"
"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 sector") OR ("state vectors"))) OR ("state vector"))))) OR ("state actors"))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"state actor\") or (((((\"state sector\") OR (\"state vectors\"))) or (\"state vector\"))))) or (\"state actors\"))*".
• Removing quotes may allow a broader search: (((( state actor ) or ((((( state sector ) OR ( state vectors ))) or ( state vector ))))) or ( state actors ))*.