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: balance de investigacion en" » "serie: balance la investigacion en"
"serie: balance de investigacion y" » "serie: balance la investigacion y"
"serie: alcance de investigacion y" » "serie: alcance la investigacion y"

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: balance de investigacion 7") or ("serie: balance de investigacion en"))) or ((("serie: balance de investigacion y") OR ("serie: alcance 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") OR ("serie: alcance 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\") OR (\"serie: alcance 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 ) OR ( serie: alcance de investigacion y )))).
• Adding a wildcard symbol may retrieve word variants: (((("serie: balance de investigacion 7") or ("serie: balance de investigacion en"))) or ((("serie: balance de investigacion y") OR ("serie: alcance de investigacion y"))))*.