Perhaps you should try some spelling variations:
"serie letras a clave." » "serie las a clave.", "serie letras la clave.", "serie letras al clave.", "serie letras y clave.", "serie letras i clave.", "serie letras una clave."
"serie actas a clave." » "serie fichas a clave.", "serie actas i clave.", "serie actas y clave.", "serie actas v clave.", "serie actas una clave."
"serie notas la clave." » "serie notas a clave.", "serie poetas la clave.", "serie notas mas clave.", "serie notas la clase.", "serie notas la llave.", "serie notas en clave.", "serie notas li clave.", "serie notas ly clave.", "serie notas luna clave."

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