Perhaps you should try some spelling variations:
"social effect model" » "social effects model", "societal effect model", "special effect model", "social effect models", "social effects models"
"social exact model" » "social etats model", "social email model", "social era model"
"social jet model" » "social je model", "social act model", "social jetlag model", "social net model", "social set model", "social jnet model", "social jset model", "social jet modele"
"social et model" » "social en model", "social e model", "social etats model", "social net model", "social set model", "social et modele"

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 ((("social et model") OR ("social jet model")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"social exact model\") OR (\"social effect model\"))) or (((\"social et model\") or (\"social jet model\"))))".
• Removing quotes may allow a broader search: (((( social exact model ) OR ( social effect model ))) or ((( social et model ) or ( social jet model )))).
• Adding a wildcard symbol may retrieve word variants: (((("social exact model") OR ("social effect model"))) or ((("social et model") or ("social jet model"))))*.