Perhaps you should try some spelling variations:
"seis estudios americanos." » "seis estudios latinoamericanos.", "los estudios americanos.", "dos estudios americanos.", "dios estudios americanos."
"serie estudios urbano." » "serie estudios urbanos.", "serie estudio urbano.", "serie estudios peruanos."
"series estudios urbano." » "series estudios urbanos.", "series estudio urbano.", "series estudios peruanos.", "tres estudios urbano.", "leyes estudios urbano.", "sociales 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 urbano.") or ((("series estudios urbano.") or ("seis estudios americanos."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("serie estudios urbano.") OR ((("series estudios urbano.") OR ("seis estudios americanos."))))*.
• Removing quotes may allow a broader search: (( serie estudios urbano. ) or ((( series estudios urbano. ) or ( seis estudios americanos. ))))*.