Perhaps you should try some spelling variations:
"social needs model" » "special needs model", "social norms model", "social needs more"
"social net model" » "social news model"
"social na model" » "social a model", "social _ model", "social dna model", "social rna model"

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