Perhaps you should try some spelling variations:
social effect » social effects, societal effect, special effect
effect model » effect models, effects model, effects models
etats model » etas model, rats model, beats model
rate model » rate models, state model, primate model

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 ((etats model) OR (rate model)) ) OR ( social effect model )).
• Adding a wildcard symbol may retrieve word variants: (( social ((etats model) or (rate model)) ) or ( social effect model ))*.