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All smiles are positive, but some smiles are more positive than others.
Messinger, Daniel S., Fogel, Alan, Dickson, K. LaurieVolume:
37
Year:
2001
Language:
english
Journal:
Developmental Psychology
DOI:
10.1037/0012-1649.37.5.642
File:
PDF, 1.36 MB
english, 2001