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