Journal Article
                        
                        Walker, S P, T D  Wachs, S  Grantham-McGregor, M M  Black, C A  Nelson, S L  Huffman, H  Baker-Henningham, S M  Chang, J D  Hamadani, B  Lozoff, and   others.  
"Inequality in early childhood: risk and protective factors for early child development." (2011) The Lancet.