Perhaps you should try some spelling variations:
"social effects models" » "special effects models", "social aspects models", "social effect models", "societal effects models", "local effects models"
"social effect model" » "societal effect model", "special effect model", "local effect model", "social effect models", "social effects model", "social effective model"

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"social effect model\") OR (\"social effects models\"))".
• Removing quotes may allow a broader search: (( social effect model ) OR ( social effects models )).
• Adding a wildcard symbol may retrieve word variants: (("social effect model") OR ("social effects models"))*.