1. T. Callen, Gross domestic product: an economy’s all. IMF. http://www.imf.org/external/pubs/ft/fandd/basics/gdp.htm . Accessed 10 Nov 2016
2. Mortality Rate, Infant, The World Bank. http://data.worldbank.org/indicator/sp.dy.imrt.in . Accessed 20 Oct 2017
3. I.C. Demetriou, P. Tzitziris, Infant mortality and economic growth: modeling by increasing returns and least squares. In: Lecture Notes in Engineering and Computer Science: Proceedings of The World Congress on Engineering 2017, WCE 2017, 5–7 July 2017, London, U.K., ed. by S.I. Ao, L. Gelman, D.W.L. Hukins, A. Hunter, A.M. Korsunsky, vol. II, pp. 543–548
4. C. Hildreth, Point estimates of ordinates of concave functions. J. Am. Stat. Assoc. 49, 598–619 (1954)
5. C. de Boor, A Practical Guide to Splines, Revised Edition (Springer, New York, 2001)