Perhaps you should try some spelling variations:
"state vectors" » "state detectors", "space vectors"
"state vector" » "space vector"
"state actor" » "state action", "state sector", "state after"
"state actors" » "state actions", "state sectors", "state afters", "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 actors") OR ((("state vectors") OR ("state vector")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"state actor\") or (((\"state actors\") or (((\"state vectors\") OR (\"state vector\"))))))".
• Removing quotes may allow a broader search: (( state actor ) or ((( state actors ) or ((( state vectors ) OR ( state vector )))))).
• Adding a wildcard symbol may retrieve word variants: (("state actor") or ((("state actors") or ((("state vectors") OR ("state vector"))))))*.