Perhaps you should try some spelling variations:
"cooperating systems" » "operating systems", "cooperation systems", "operating system"
"operations systems" » "operations system", "operational systems", "operating systems"
"cooperative systems" » "cooperation systems"

Try widening your search to All Fields.

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: (((("cooperating systems") OR ("cooperative systems"))) OR ("operations systems")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"cooperating systems\") OR (\"cooperative systems\"))) or (\"operations systems\"))".
• Removing quotes may allow a broader search: (((( cooperating systems ) OR ( cooperative systems ))) or ( operations systems )).
• Adding a wildcard symbol may retrieve word variants: (((("cooperating systems") OR ("cooperative systems"))) or ("operations systems"))*.