Perhaps you should try some spelling variations:
"dios estudios americanos." » "dios estudios latinoamericanos.", "dos estudios americanos.", "los estudios americanos.", "otros estudios americanos."
"series estudios urbano." » "serie estudios urbano.", "tres estudios urbano.", "leyes estudios urbano.", "series estudios urbanos.", "series estudio urbano.", "series estudios peruanos."
"seis estudios urbano." » "seis estudios urbanos.", "seis estudio urbano.", "seis estudios peruanos.", "los estudios urbano.", "dos estudios urbano.", "pons 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: (((("series estudios urbano.") OR ("seis estudios urbano."))) or ("dios estudios americanos."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("series estudios urbano.") OR ("seis estudios urbano."))) OR ("dios estudios americanos."))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"series estudios urbano.\") OR (\"seis estudios urbano.\"))) or (\"dios estudios americanos.\"))*".
• Removing quotes may allow a broader search: (((( series estudios urbano. ) OR ( seis estudios urbano. ))) or ( dios estudios americanos. ))*.