Perhaps you should try some spelling variations:
"serie lecturas de clacso." » "serie letras de clacso.", "serie lectura de clacso."
"serie cartas de clase." » "serie actas de clase.", "serie arte de clase.", "serie art de clase.", "serie carta de clase.", "serie cartas la clase."
"serie notas de clase." » "serie actas de clase.", "serie notas la clase."

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("serie cartas de clase.") OR ("serie notas de clase."))) OR ("serie lecturas de clacso."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"serie cartas de clase.\") OR (\"serie notas de clase.\"))) or (\"serie lecturas de clacso.\"))~".
• Removing quotes may allow a broader search: (((( serie cartas de clase. ) OR ( serie notas de clase. ))) or ( serie lecturas de clacso. ))~.
• Adding a wildcard symbol may retrieve word variants: (((("serie cartas de clase.") OR ("serie notas de clase."))) or ("serie lecturas de clacso."))*.