Perhaps you should try some spelling variations:
"spectral effects model" » "special effects model", "sectoral effects model", "central effects model", "spectral effects models", "spectral effect models"
"special respect model" » "special aspects model", "special report model", "special request model", "special aspect model", "special respective model", "special respect de"
"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 ((("spectral effects model") OR ("special respect model")))).
• Removing quotes may allow a broader search: (((( social exact model ) or ( social etats model ))) or ((( spectral effects model ) or ( special respect model )))).
• Adding a wildcard symbol may retrieve word variants: (((("social exact model") or ("social etats model"))) or ((("spectral effects model") or ("special respect model"))))*.