Perhaps you should try some spelling variations:
"social effective model" » "social affective model", "special effective model", "local effective model", "social effects model", "social effectsive model", "societal effective model"
"social effect models" » "social effects models", "societal effect models", "special effect 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 effective model") OR ("social effect models"))))*.
• Removing quotes may allow a broader search: (( social exact model ) or ((( social effective model ) or ( social effect models ))))*.