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