Perhaps you should try some spelling variations:
"seis estudios peruanos." » "seis estudios urbanos.", "seis estudios americanos.", "seis estudios ensayos.", "los estudios peruanos.", "dos estudios peruanos.", "dios estudios peruanos."
"tres studies hispanic." » "tres estudios hispanicos.", "tres estudios hispano.", "tres studies spain.", "tres estudios hispanic.", "cases studies hispanic.", "tres ataudes hispanic."
"series estudios urbano." » "serie estudios urbano.", "tres estudios urbano.", "leyes estudios urbano.", "series estudios urbanos.", "series estudio urbano.", "series estudios hispano."

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: (((("seis estudios peruanos.") or ("series estudios urbano."))) or ("tres studies hispanic."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("seis estudios peruanos.") OR ("series estudios urbano."))) OR ("tres studies hispanic.")).
• Removing quotes may allow a broader search: (((( seis estudios peruanos. ) or ( series estudios urbano. ))) or ( tres studies hispanic. )).
• Adding a wildcard symbol may retrieve word variants: (((("seis estudios peruanos.") or ("series estudios urbano."))) or ("tres studies hispanic."))*.