Perhaps you should try some spelling variations:
"serie: balance de investigacion por" » "serie: balance de investigacion sobre", "serie: balance de investigacion como", "serie: balance de investigacion e", "serie: balance la investigacion por"
"serie: alcance de investigacion en" » "serie: alcance la investigacion en"
"serie: balance de investigacion y" » "serie: balance 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 por") or ("serie: alcance 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 por") OR ("serie: alcance de investigacion en"))) OR ("serie: balance de investigacion y")).
• Removing quotes may allow a broader search: (((( serie: balance de investigacion por ) or ( serie: alcance de investigacion en ))) or ( serie: balance de investigacion y )).
• Adding a wildcard symbol may retrieve word variants: (((("serie: balance de investigacion por") or ("serie: alcance de investigacion en"))) or ("serie: balance de investigacion y"))*.