Taagepera, Rein (1979). «Size and Duration of Empires: Growth-Decline Curves, 600 B.C. to 600 A.D». Social Science History (Duke University Press) 3 (3/4): 125. JSTOR1170959. doi:10.2307/1170959.
Durand, John D. (1977). «Historical Estimates of World Population: An Evaluation». Population and Development Review3 (3): 253. JSTOR1971891. doi:10.2307/1971891.
Taagepera, Rein (1979). «Size and Duration of Empires: Growth-Decline Curves, 600 B.C. to 600 A.D». Social Science History (Duke University Press) 3 (3/4): 125. JSTOR1170959. doi:10.2307/1170959.
Durand, John D. (1977). «Historical Estimates of World Population: An Evaluation». Population and Development Review3 (3): 253. JSTOR1971891. doi:10.2307/1971891.