Perhaps you should try some spelling variations:
"series estudios americanoss." » "series estudios americanos.", "series estados americanos.", "series estudios africanos.", "serie estudios americanoss.", "seis estudios americanoss.", "tres estudios americanoss."
"dios estudios peruanos." » "dios estudios americanos.", "dios estudios ensayos.", "dios estudios cervantinos.", "los estudios peruanos.", "otros estudios peruanos.", "altos estudios peruanos."
"dos estudios urbanos." » "los estudios urbanos."

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: (((("series estudios americanoss.") OR ("dos estudios urbanos."))) OR ("dios estudios peruanos."))~.
• Removing quotes may allow a broader search: (((( series estudios americanoss. ) or ( dos estudios urbanos. ))) or ( dios estudios peruanos. ))~.
• Adding a wildcard symbol may retrieve word variants: (((("series estudios americanoss.") or ("dos estudios urbanos."))) or ("dios estudios peruanos."))*.