Perhaps you should try some spelling variations:
"social effect model" » "social effects model", "societal effect model", "special effect model", "social effects models", "social effective model"
"social effect models" » "social effects models", "societal effect models", "special effect models", "social effects modelss", "social effective models"
"social exact model" » "social etats model", "social et model", "social email 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 effect models"))))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"social exact model\") or (((\"social effect model\") OR (\"social effect models\"))))*".
• Removing quotes may allow a broader search: (( social exact model ) or ((( social effect model ) OR ( social effect models ))))*.