Perhaps you should try some spelling variations:
"special effect model" » "special effects model", "spectral effects model", "special respect model", "special effects models", "special effective model"
"special effect models" » "special effects models", "spectral effects models", "special respect models", "special effects modelss", "special effective models"
"social effect model" » "social effects model", "societal effect model", "local effect model", "social effects models", "social effective model"
"social exact model" » "social etats model", "social et model", "social email 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 effect model"))) OR ((("special effect model") OR ("special effect models")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"social exact model\") or (\"social effect model\"))) or (((\"special effect model\") OR (\"special effect models\"))))".
• Removing quotes may allow a broader search: (((( social exact model ) or ( social effect model ))) or ((( special effect model ) OR ( special effect models )))).
• Adding a wildcard symbol may retrieve word variants: (((("social exact model") or ("social effect model"))) or ((("special effect model") OR ("special effect models"))))*.