Perhaps you should try some spelling variations:
"serie estudios americanos." » "serie estudios latinoamericanos."
"tres estudios peruanos." » "tres estudios ensayos.", "tres estudios cervantinos.", "otros estudios peruanos.", "los estudios peruanos.", "dos estudios peruanos."
"serie estudios urbanos." » "serie estudios urbano."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("serie estudios americanos.") or ("tres estudios peruanos."))) or ("serie estudios urbanos."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("serie estudios americanos.") OR ("tres estudios peruanos."))) OR ("serie estudios urbanos."))*.
• Removing quotes may allow a broader search: (((( serie estudios americanos. ) or ( tres estudios peruanos. ))) or ( serie estudios urbanos. ))*.