Perhaps you should try some spelling variations:
"progreso tecnico artisticas methods." » "progreso tecnicas artisticas methods.", "progreso tecnica artistica methods.", "progreso tecnico tacticas methods.", "progresos tecnicos artisticas methods.", "progreso tecnologico artisticas methods.", "progreso economico artisticas methods."
"proceso control statistical methods." » "process control statistical methods.", "proceso contra statistical methods.", "proceso contralos statistical methods.", "proceso control statistics methods.", "proceso control estadisticas methods."

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("proceso control statistical methods.") or ("progreso tecnico artisticas methods."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("proceso control statistical methods.") OR ("progreso tecnico artisticas methods.")).
• Removing quotes may allow a broader search: (( proceso control statistical methods. ) or ( progreso tecnico artisticas methods. )).
• Adding a wildcard symbol may retrieve word variants: (("proceso control statistical methods.") or ("progreso tecnico artisticas methods."))*.