Perhaps you should try some spelling variations:
"seis estudios americanos." » "seis estudios latinoamericanos.", "los estudios americanos.", "dos estudios americanos.", "dios estudios americanos."
"series estudios urbano." » "serie estudios urbano.", "tres estudios urbano.", "leyes estudios urbano.", "series estudio urbano.", "series estudios peruanos.", "series estudios hispano."
"series estudios urbanos." » "serie estudios urbanos.", "tres estudios urbanos.", "leyes estudios urbanos.", "series estudio urbanos.", "series estudios peruanoss.", "series estudios hispanos."

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 urbano.") OR ("series estudios urbanos."))) or ("seis estudios americanos."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("series estudios urbano.") OR ("series estudios urbanos."))) OR ("seis estudios americanos."))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"series estudios urbano.\") OR (\"series estudios urbanos.\"))) or (\"seis estudios americanos.\"))*".
• Removing quotes may allow a broader search: (((( series estudios urbano. ) OR ( series estudios urbanos. ))) or ( seis estudios americanos. ))*.