Perhaps you should try some spelling variations:
"state factors" » "states factors", "state factor", "state factory"
"state actions" » "state action", "state reactions", "state functions"
"state actor" » "state action", "state sector", "state after"
"state actors" » "state actions", "state sectors", "state afters"

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