Perhaps you should try some spelling variations:
"tres estudios peruanoss." » "tres estudios peruanos.", "los estudios peruanoss.", "dos estudios peruanoss.", "dios estudios peruanoss."
"otros estudios peruanoss." » "otros estudios peruanos.", "los estudios peruanoss.", "dos estudios peruanoss.", "etnicos estudios peruanoss."
"series estudios urbanos." » "serie estudios urbanos.", "seis estudios urbanos.", "leyes estudios urbanos.", "series estudios urbano."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("tres estudios peruanoss.") or ("otros estudios peruanoss."))) or ("series estudios urbanos."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("tres estudios peruanoss.") OR ("otros estudios peruanoss."))) OR ("series estudios urbanos.")).
• Removing quotes may allow a broader search: (((( tres estudios peruanoss. ) or ( otros estudios peruanoss. ))) or ( series estudios urbanos. )).
• Adding a wildcard symbol may retrieve word variants: (((("tres estudios peruanoss.") or ("otros estudios peruanoss."))) or ("series estudios urbanos."))*.