Perhaps you should try some spelling variations:
"seis estudios americanos." » "seis estudios latinoamericanos.", "los estudios americanos.", "dos estudios americanos.", "dios estudios americanos."
"series estudios urbanos." » "serie estudios urbanos.", "tres estudios urbanos.", "leyes estudios urbanos."
"otros estudios urbanos." » "los estudios urbanos.", "dos estudios urbanos.", "etnicos estudios urbanos."

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

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