 The uniqueness of the child–father attachment relationship: Father ’ s sensitive and challenging play as a pivotal variable in a 16-year longitudinal study.
<fluency>  The uniqueness of the child–father attachment relationship: Father ’ s sensitive and challenging play as a pivotal variable in a 16-year longitudinal study.
 The uniqueness of the child–father attachment relationship: Father ' s sensitive and challenging play as a pivotal variable in a 16-year longitudinal study.