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 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"

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