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