Perhaps you should try some spelling variations:
"memoria retos sociales." » "memoria efectos sociales.", "memoria sujetos sociales.", "memoria grupos sociales.", "memoria rota sociales.", "memoria reto sociales.", "memoria retos socioes.", "memoria jews sociales."
"memoria retos social." » "memoria rota social.", "memoria reto social.", "memoria retos socio.", "memoria jews social."
"memoria ethos social." » "memoria dos social.", "memoria giros social."

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