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