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

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