Perhaps you should try some spelling variations:
"social effect model" » "social effects model", "societal effect model", "special effect model", "social effect models", "social effects models"
"social exact model" » "social etats model", "social et model", "social email model"
"social beats model" » "social beasts model", "social etats model", "social bots model", "social seats model", "social nets model"

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 effect model"))) OR ("social beats model"))*.
• Removing quotes may allow a broader search: (((( social exact model ) or ( social effect model ))) or ( social beats model ))*.