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