Perhaps you should try some spelling variations:
"tres estudios criticos." » "tres estudios juridicos.", "otros estudios criticos.", "los estudios criticos.", "dos estudios criticos."
"series estudios hispanos." » "series estudios hispano.", "series estudios hispanicos.", "series estudios espanoles.", "serie estudios hispanos.", "leyes estudios hispanos.", "sociales estudios hispanos."
"seis estudios hispanos." » "seis estudios hispano.", "seis estudios hispanicos.", "seis estudios espanoles.", "los estudios hispanos.", "dos estudios hispanos.", "dios estudios hispanos."

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