Perhaps you should try some spelling variations:
"serie: balance de investigacion 7" » "serie: balance la investigacion 7", "serie: balance de investigacion e", "serie: balance de investigacion por", "serie: balance de investigaciones y", "serie: alcance de investigacion 7"
"serie: balance de investigacion en" » "serie: balance la investigacion en", "serie: alcance de investigacion en"
"serie: balance de investigacion y" » "serie: balance la investigacion y", "serie: alcance de investigacion y"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("serie: balance de investigacion 7") OR ("serie: balance de investigacion en"))) or ("serie: balance de investigacion y"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("serie: balance de investigacion 7") OR ("serie: balance de investigacion en"))) OR ("serie: balance de investigacion y"))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"serie: balance de investigacion 7\") OR (\"serie: balance de investigacion en\"))) or (\"serie: balance de investigacion y\"))*".
• Removing quotes may allow a broader search: (((( serie: balance de investigacion 7 ) OR ( serie: balance de investigacion en ))) or ( serie: balance de investigacion y ))*.