Perhaps you should try some spelling variations:
"series estudios peruanoss." » "series estudios peruanos.", "series estudios urbanos.", "serie estudios peruanoss.", "seis estudios peruanoss.", "leyes estudios peruanoss.", "serie estudioss peruanoss.", "senales estudios peruanoss."
"tres estudios etnicos." » "tres estudios criticos.", "tres estudios biblicos.", "otros estudios etnicos.", "los estudios etnicos.", "dos estudios etnicos."
"series estudio urbano." » "serie estudio urbano.", "serie estudios urbano.", "senales estudio urbano.", "series estudios urbano.", "series estudios urbanos.", "series espacio urbano."

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: (((("series estudios peruanoss.") or ("tres estudios etnicos."))) or ("series estudio urbano."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("series estudios peruanoss.") OR ("tres estudios etnicos."))) OR ("series estudio urbano.")).
• Removing quotes may allow a broader search: (((( series estudios peruanoss. ) or ( tres estudios etnicos. ))) or ( series estudio urbano. )).
• Adding a wildcard symbol may retrieve word variants: (((("series estudios peruanoss.") or ("tres estudios etnicos."))) or ("series estudio urbano."))*.