Perhaps you should try some spelling variations:
"seis estudios urbano." » "seis estudios urbanos.", "seis estudios peruanos.", "seis d'estudis urbans.", "los estudios urbano.", "dos estudios urbano.", "dios estudios urbano."
"series estudio urbano." » "series estudios urbano.", "serie estudio urbano.", "serie estudios urbano.", "series estudios urbanos.", "series espacio urbano."
"tres estudios hispano." » "otros estudios hispano.", "los estudios hispano.", "dos estudios hispano.", "tres estudios hispana.", "tres estudios hispanic."

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