De Sanctis, Vincenzo, et al. “Cross-Sectional Observational Study of Nipple and Areola Changes During Pubertal Development and After Menarche in 313 Italian Girls”. Acta Biomedica Atenei Parmensis, vol. 87, no. 2, Sept. 2016, pp. 177-83, https://www.mattioli1885journals.com/index.php/actabiomedica/article/view/5496.