Perhaps you should try some spelling variations:
"sectoral effects model" » "central effects model", "temporal effects model", "structural effects model", "sectoral effects models", "sectoral effect models"
"special effect model" » "special effects model", "spectral effects model", "social effects model", "special effect models", "special effects models", "special effective model"
"social exact model" » "social effect model", "social et model", "social email model"
"social etats model" » "social ethics model", "social etas model", "social rats model", "social beats 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 ("social etats model"))) OR ((("special effect model") OR ("sectoral effects model")))).
• Removing quotes may allow a broader search: (((( social exact model ) or ( social etats model ))) or ((( special effect model ) or ( sectoral effects model )))).
• Adding a wildcard symbol may retrieve word variants: (((("social exact model") or ("social etats model"))) or ((("special effect model") or ("sectoral effects model"))))*.