Perhaps you should try some spelling variations:
"tres estudios peruanos." » "tres estudios americanos.", "tres estudios ensayos.", "tres estudios cervantinos.", "otros estudios peruanos.", "los estudios peruanos.", "dos estudios peruanos."
"series estudioss urbano." » "serie estudios urbano.", "seis estudios urbano.", "serie estudio urbano.", "series estudios urbano.", "series estudio urbano.", "serie estudioss urbano.", "seis estudioss urbano.", "leyes estudioss urbano."
"series estudios urbanos." » "serie estudios urbanos.", "seis estudios urbanos.", "leyes estudios urbanos."

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

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