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