Perhaps you should try some spelling variations:
"social etas model" » "social etats model", "social eclas model", "social et model", "social keras model", "social gas model", "social das model"
"social net model" » "social news model", "social needs model"
"social na model" » "social a model", "social _ model", "social dna model", "social rna 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 etas model") OR ((("social na model") OR ("social net model")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"social etas model\") or (((\"social na model\") OR (\"social net model\"))))".
• Removing quotes may allow a broader search: (( social etas model ) or ((( social na model ) OR ( social net model )))).
• Adding a wildcard symbol may retrieve word variants: (("social etas model") or ((("social na model") OR ("social net model"))))*.