Perhaps you should try some spelling variations:
"improving worker performance series." » "improving worker performance studies.", "improving worker performance size.", "improving work performance series.", "improving market performance series.", "improving poor performance series.", "improving water performance series."
"improving ict performance measures." » "improving act performance measures.", "improving iot performance measures.", "improving lift performance measures.", "improving co performance measures.", "improving eco performance measures.", "improving its performance measures."

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: (("improving worker performance series.") OR ("improving ict performance measures."))~.
• Removing quotes may allow a broader search: (( improving worker performance series. ) or ( improving ict performance measures. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving worker performance series.") or ("improving ict performance measures."))*.