Perhaps you should try some spelling variations:
"state vectors" » "state actors", "state detectors"
"state factors" » "states factors", "state actors", "state factor"
"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 ("state action"))) OR ((("state vectors") OR ("state vector"))))) OR ("state factors")).
• Removing quotes may allow a broader search: (((((( state actor ) or ( state action ))) or ((( state vectors ) or ( state vector ))))) or ( state factors )).
• Adding a wildcard symbol may retrieve word variants: (((((("state actor") or ("state action"))) or ((("state vectors") or ("state vector"))))) or ("state factors"))*.