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

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