Perhaps you should try some spelling variations:
"proceso control estadistico factor." » "proceso control statistical factor.", "proceso control estadistico con.", "proceso contra estadistico factor.", "proceso contralos estadistico factor.", "proces contre estadistico factor."
"process control statistics methods." » "process control statistical methods.", "process control estadistica methods.", "process century statistics methods.", "process control statistics methodology.", "procesos control statistics methods.", "procesal control statistics methods."

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: (("process control statistics methods.") OR ("proceso control estadistico factor."))~.
• Removing quotes may allow a broader search: (( process control statistics methods. ) or ( proceso control estadistico factor. ))~.
• Adding a wildcard symbol may retrieve word variants: (("process control statistics methods.") or ("proceso control estadistico factor."))*.