Perhaps you should try some spelling variations:
"proces estudio estadistico factor." » "proces estudio periodistico factor.", "proces estudio estadistico con.", "procesal estudio estadistico factor.", "artes estudio estadistico factor.", "propia estudio estadistico factor."
"process control statistical methods." » "procesos control statistical methods.", "proceso control statistical methods.", "procesal control statistical methods.", "process control statistics methods.", "process control estadisticas 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 statistical methods.") OR ("proces estudio estadistico factor."))~.
• Removing quotes may allow a broader search: (( process control statistical methods. ) or ( proces estudio estadistico factor. ))~.
• Adding a wildcard symbol may retrieve word variants: (("process control statistical methods.") or ("proces estudio estadistico factor."))*.