PMID 16298218. doi:10.1016/S0140-6736(05)67574-5. CS1 maint: Multiple names: authors list (link) ↑ Walker SP, Chang SM, Powell CA, Simonoff E, Grantham-McGregor SM (September 2006). "Effects of psychosocial stimulation and dietary supplementation in early childhood on psychosocial functioning in late adolescence: follow-up of randomised controlled trial".