Perhaps you should try some spelling variations:
"social exact model" » "social effect model", "social et model", "social email model"
"social etats model" » "social ethics model", "social etas model", "social rats model", "social beats model"
"social net model" » "social news model", "social na model", "social needs model"

Try widening your search to All Fields.

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

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