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 estudios urbanos.", "series estudios peruanos.", "series estudios hispano.", "serie estudioss urbano.", "senales estudios urbano."
"series estudio urbano." » "serie estudio urbano.", "serie estudios urbano.", "senales estudio urbano.", "series estudios urbanos.", "series espacio urbano."

You may be able to get more results by adjusting your search query.

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