Perhaps you should try some spelling variations:
"social effect models" » "social effects models", "societal effect models", "special effect models"
"social net model" » "social news model", "social na model", "social needs model"
"social self model" » "social self made", "social self modeling", "social belief 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 net model") OR ("social self model"))) OR ("social effect models")).
• Removing quotes may allow a broader search: (((( social net model ) or ( social self model ))) or ( social effect models )).
• Adding a wildcard symbol may retrieve word variants: (((("social net model") or ("social self model"))) or ("social effect models"))*.