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