Perhaps you should try some spelling variations:
"societal effect models" » "societal effects models", "social effects models", "society effects models"
"special effects model" » "special effects models"
"social exact model" » "social effect model", "social etats model", "social et model"

Try widening your search to All Fields.

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 ("societal effect models"))) OR ("special effects model")).
• Removing quotes may allow a broader search: (((( social exact model ) or ( societal effect models ))) or ( special effects model )).
• Adding a wildcard symbol may retrieve word variants: (((("social exact model") or ("societal effect models"))) or ("special effects model"))*.