Perhaps you should try some spelling variations:
"tres estudios urbano." » "tres estudio urbano.", "tres estudios peruanos.", "tres estudios hispano.", "otros estudios urbano.", "los estudios urbano.", "dos estudios urbano."
"series estudios urbano." » "series estudio urbano.", "series estudios peruanos.", "series estudios hispano.", "serie estudios urbano.", "seis estudios urbano.", "leyes estudios urbano."
"series estudios urbanos." » "series estudio urbanos.", "series estudios peruanoss.", "series estudios hispanos.", "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: (("tres estudios urbano.") or ((("series estudios urbano.") OR ("series estudios urbanos."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tres estudios urbano.") OR ((("series estudios urbano.") OR ("series estudios urbanos.")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"tres estudios urbano.\") or (((\"series estudios urbano.\") OR (\"series estudios urbanos.\"))))".
• Removing quotes may allow a broader search: (( tres estudios urbano. ) or ((( series estudios urbano. ) OR ( series estudios urbanos. )))).
• Adding a wildcard symbol may retrieve word variants: (("tres estudios urbano.") or ((("series estudios urbano.") OR ("series estudios urbanos."))))*.