Perhaps you should try some spelling variations:
social effect » social effects, societal effect, special effect
effect model » effect models, effects model, effects models
hats model » rats model, charts model, habits model
etas model » keras model, gas model, das 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 effect model ) OR ( social ((hats model) OR (etas model)) )).
• Adding a wildcard symbol may retrieve word variants: (( social effect model ) or ( social ((hats model) or (etas model)) ))*.