46Castaldo, Adriana, Saskia Gent, Gunjan Sondhi, and Ann Whitehead. "Child migration in national surveys."Development Research Centre on Migration, Globalisation and Poverty Working Paper No. T-28 (2009).
47Olken, Benjamin A, and Monica Singhal. "Informal taxation."Harvard Kennedy School Faculty Research Working Paper No. 09-033 (2009).