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