Perhaps you should try some spelling variations:
"serie cartas de clase." » "serie arte de clase.", "serie notas de clase.", "serie art de clase.", "serie artes de clase.", "serie arts de clase.", "serie cartas de clacso.", "serie cartas la clase."
"serie actas de clases." » "serie letras de clases.", "serie fichas de clases.", "serie actas de bases.", "serie actas del clases.", "serie actas de clacsos.", "serie actas la clases."
"serie carta de clase." » "serie arte de clase.", "serie art de clase.", "serie carta de clacso.", "serie carta la 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 actas de clases.") or ((("serie cartas de clase.") OR ("serie carta de clase."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("serie actas de clases.") OR ((("serie cartas de clase.") OR ("serie carta de clase.")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"serie actas de clases.\") or (((\"serie cartas de clase.\") OR (\"serie carta de clase.\"))))".
• Removing quotes may allow a broader search: (( serie actas de clases. ) or ((( serie cartas de clase. ) OR ( serie carta de clase. )))).
• Adding a wildcard symbol may retrieve word variants: (("serie actas de clases.") or ((("serie cartas de clase.") OR ("serie carta de clase."))))*.