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