Perhaps you should try some spelling variations:
"tres estadios urbano." » "tres estudios urbano.", "tres estudio urbano.", "tres espacios urbanos.", "tres estados urbano.", "de estadios urbano."
"series estudios urbanos." » "serie estudios urbanos.", "tres estudios urbanos.", "leyes estudios urbanos."
"seis estudios urbanos." » "los estudios urbanos.", "dos estudios urbanos.", "dios estudios urbanos."

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: (("tres estadios urbano.") or ((("series estudios urbanos.") OR ("seis estudios urbanos."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tres estadios urbano.") OR ((("series estudios urbanos.") OR ("seis estudios urbanos.")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"tres estadios urbano.\") or (((\"series estudios urbanos.\") OR (\"seis estudios urbanos.\"))))".
• Removing quotes may allow a broader search: (( tres estadios urbano. ) or ((( series estudios urbanos. ) OR ( seis estudios urbanos. )))).
• Adding a wildcard symbol may retrieve word variants: (("tres estadios urbano.") or ((("series estudios urbanos.") OR ("seis estudios urbanos."))))*.