Perhaps you should try some spelling variations:
"series estudios peruanoss." » "series estudios peruanos.", "serie estudios peruanoss.", "tres estudios peruanoss.", "leyes estudios peruanoss."
"seis estudios urbanos." » "seis estudio urbanos.", "seis estudios peruanoss.", "seis estudios hispanos.", "los estudios urbanos.", "dios estudios urbanos.", "pons estudios urbanos."
"dos estudios urbano." » "dos estudio urbano.", "dos estudios peruanos.", "dos estudios hispano.", "los 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 peruanoss.") or ("seis estudios urbanos."))) or ("dos estudios urbano."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("series estudios peruanoss.") OR ("seis estudios urbanos."))) OR ("dos estudios urbano."))*.
• Removing quotes may allow a broader search: (((( series estudios peruanoss. ) or ( seis estudios urbanos. ))) or ( dos estudios urbano. ))*.