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"
"societal effect model" » "societal effects model", "social effects model", "society effects model", "societal effect models", "societal effects models", "societal effective model"
"special effect model" » "special effects model", "special respect model", "social effects model", "special effect models", "special effects models", "special effective model"
"social effect model" » "social effects model", "local effect model", "focal effect model", "social effect models", "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 ("societal effect model"))) OR ((("special effect model") OR ("spectral effects model")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"social exact model\") or (((((\"social effect model\") or (\"societal effect model\"))) or (((\"special effect model\") OR (\"spectral effects model\"))))))".
• Removing quotes may allow a broader search: (( social exact model ) or ((((( social effect model ) or ( societal effect model ))) or ((( special effect model ) OR ( spectral effects model )))))).
• Adding a wildcard symbol may retrieve word variants: (("social exact model") or ((((("social effect model") or ("societal effect model"))) or ((("special effect model") OR ("spectral effects model"))))))*.