Perhaps you should try some spelling variations:
"seis estudios americanos." » "seis estudios latinoamericanos.", "los estudios americanos.", "dos estudios americanos.", "pons estudios americanos."
"dios estudios americanos." » "dios estudios latinoamericanos.", "dos estudios americanos.", "los estudios americanos.", "otros estudios americanos."
"serie estudios urbano." » "serie estudios urbanos.", "serie estudio urbano.", "serie estudios peruanos."

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