Santillán-Salgado, Roberto J., et al. “On the Relations Among CO2 Emissions, Gross Domestic Product, Energy Consumption, Electricity Use, Urbanization, and Income Inequality for a Sample of 134 Countries”. International Journal of Energy Economics and Policy, vol. 10, no. 6, Oct. 2020, pp. 195-07, https://econjournals.com/index.php/ijeep/article/view/10070.