Perhaps you should try some spelling variations:
"clases sociedades contemporaneas ;" » "clases sociedade contemporanea ;" (Expand Search), "clases sociedad contemporanea ;" (Expand Search), "clases social contemporanea ;" (Expand Search), "las sociedades contemporaneas ;" (Expand Search), "nas sociedades contemporaneas ;" (Expand Search), "das sociedades contemporaneas ;" (Expand Search)
"clases sociales contemporaneos ;" » "clases social contemporanea ;" (Expand Search), "clases politicos contemporaneos ;" (Expand Search), "clausulas sociales contemporaneos ;" (Expand Search)

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• Performing a fuzzy search may retrieve terms with similar spellings: (("clases sociales contemporaneos ;") OR ("clases sociedades contemporaneas ;"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"clases sociales contemporaneos ;\") OR (\"clases sociedades contemporaneas ;\"))".
• Removing quotes may allow a broader search: (( clases sociales contemporaneos ; ) OR ( clases sociedades contemporaneas ; )).
• Adding a wildcard symbol may retrieve word variants: (("clases sociales contemporaneos ;") OR ("clases sociedades contemporaneas ;"))*.