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 ethos sociales.", "memoria retos socioes."
"memoria gerona social." » "memoria personal social.", "memoria veronica social.", "memoria bernal social.", "memoria persona social.", "memoria gerencia social.", "memoria arena social."
"memoria retos social." » "memoria rota social.", "memoria reto social.", "memoria ethos social.", "memoria retos socio."

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 gerona social."))) or ("memoria retos sociales."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("memoria retos social.") OR ("memoria gerona social."))) OR ("memoria retos sociales.")).
• Removing quotes may allow a broader search: (((( memoria retos social. ) or ( memoria gerona social. ))) or ( memoria retos sociales. )).
• Adding a wildcard symbol may retrieve word variants: (((("memoria retos social.") or ("memoria gerona social."))) or ("memoria retos sociales."))*.