Perhaps you should try some spelling variations:
"tres estudios hispanic." » "tres estudios hispanicos.", "tres estudios hispano.", "tres studies hispanic.", "otros estudios hispanic.", "los estudios hispanic.", "dios estudios hispanic."
"dos estudios urbano." » "dos estudios urbanos.", "dos estudio urbano.", "dos estudios peruanos.", "los estudios urbano."
"series estudios urbano." » "series estudios urbanos.", "series estudio urbano.", "series estudios peruanos.", "serie estudios urbano.", "seis estudios urbano.", "leyes 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: (((("dos estudios urbano.") or ("series estudios urbano."))) or ("tres estudios hispanic."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("dos estudios urbano.") OR ("series estudios urbano."))) OR ("tres estudios hispanic.")).
• Removing quotes may allow a broader search: (((( dos estudios urbano. ) or ( series estudios urbano. ))) or ( tres estudios hispanic. )).
• Adding a wildcard symbol may retrieve word variants: (((("dos estudios urbano.") or ("series estudios urbano."))) or ("tres estudios hispanic."))*.