Perhaps you should try some spelling variations:
"dios estudios peruanos." » "dios estudios americanos.", "dios estudios ensayos.", "dios estudios cervantinos.", "dos estudios peruanos.", "los estudios peruanos.", "otros estudios peruanos."
"leyes estudios urbanos." » "series estudios urbanos.", "los estudios urbanos.", "tres estudios urbanos."
"seis estudios mercantiles." » "los estudios mercantiles.", "dos estudios mercantiles.", "pons estudios mercantiles."

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("leyes estudios urbanos.") or ((("seis estudios mercantiles.") or ("dios estudios peruanos."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("leyes estudios urbanos.") OR ((("seis estudios mercantiles.") OR ("dios estudios peruanos.")))).
• Removing quotes may allow a broader search: (( leyes estudios urbanos. ) or ((( seis estudios mercantiles. ) or ( dios estudios peruanos. )))).
• Adding a wildcard symbol may retrieve word variants: (("leyes estudios urbanos.") or ((("seis estudios mercantiles.") or ("dios estudios peruanos."))))*.