Perhaps you should try some spelling variations:
"ferre retratos de clacso." » "ferre retrats de clacso.", "serie retratos de clacso.", "sobre retratos de clacso.", "ferre retrato de clacso.", "ferre contratos de clacso."
"serie cartas la clase." » "serie actas la clase.", "serie arte la clase.", "serie notas la clase.", "serie cartas a clase.", "serie carta la clase.", "serie cartas una clase."
"serie detras de clase." » "serie letras de clase.", "serie lecturas de clase.", "serie retratos de clase."

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: (("serie cartas la clase.") or ((("ferre retratos de clacso.") or ("serie detras de clase."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("serie cartas la clase.") OR ((("ferre retratos de clacso.") OR ("serie detras de clase.")))).
• Removing quotes may allow a broader search: (( serie cartas la clase. ) or ((( ferre retratos de clacso. ) or ( serie detras de clase. )))).
• Adding a wildcard symbol may retrieve word variants: (("serie cartas la clase.") or ((("ferre retratos de clacso.") or ("serie detras de clase."))))*.