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