Lestari, Sri, et al. “Haemoglobin Levels of Adolescent Girls Aged 11-19 Years in North Sumatera Are Correlated With Socio-Economic Status and Menstrual Cycle Duration”. Pakistan Journal of Nutrition, vol. 19, no. 3, Feb. 2020, pp. 122–126, https://doi.org/10.3923/pjn.2020.122.126.